Vermont Sen. Bernie Sanders is stirring up a lot of enthusiasm among liberal activists as he campaigns for the 2016 Democratic presidential nomination. But will he be able to convert that energy into a viable national campaign that can take on Hillary Clinton, the party's dominant frontrunner?
There's certainly no shortage of excitement surrounding Sanders' bid. The senator has drawn crowds in excess of 10,000 at multiple rallies around the country. And on Wednesday, more than 100,000 people RSVPed to attend a gathering of Sanders supporters, watching as the candidate's speech in a Washington, D.C. apartment was broadcast live to thousands of other parties nationwide.
It was an impressive turnout, and Sanders' campaign suggested it came together without much heavy lifting on their part.
"100,000 people in 50 states is a demonstration of how much we can build, and how inexpensively we can build it," Sanders' chief strategist, Tad Devine, told CBS News. "We didn't spend millions of dollars to pull that event off on Wednesday."
According to public polling data, Sanders has emerged from the pack as the strongest Democratic rival to Clinton. His campaign is eager to build on that momentum, but they admit they have their work cut out for them.
"I think we were initially surprised by how much interest and excitement there was," Devine said. "Once these big crowds started appearing, I don't think we were as surprised as we were before...We're obviously very pleased about it, [but] this is really just the beginning. In order for this to succeed, we're going to have to make it much bigger. Now the test is can we put together a ground organization in early states and get ballot access everywhere."
Not everyone is convinced Team Sanders can make that happen, though. Clinton still has a lot of assets on her side, including more money, a more robust organization, and more endorsements from elected officials. That foundation is tough to discount. There are also signs Sanders may have trouble wooing core Democratic constituencies like Black and Latino voters, who are drawn to his populist message on income inequality but need to hear more about his stance on institutional racism, police reform, immigration reform, and other issues.
There would also be the uphill battle to convince Democratic Party officials that nominating a self-described "independent socialist" wouldn't doom the party in the 2016 general election.
With that in mind, here are five reasons Clinton's campaign isn't sweating the "Sanders surge" - at least not yet.
The first and perhaps most obvious laurel on which Clinton's campaign can rest is her continued strength in primary polls.
It's true that Sanders has gained ground in recent state and national polls. It's also true that he's all but cornered the market on Democratic voters seeking an alternative to the Clinton juggernaut. But even with his apparent momentum, Sanders is still polling far behind Clinton, who still nets a comfortable majority of primary voters in national surveys.
In a Quinnipiac poll released Thursday, for example, Clinton held a commanding lead at 55 percent among Democratic primary voters nationwide, while Sanders finished a distant second at 17 percent. Vice President Joe Biden, who has not declared a bid, was at 13 percent, and no other Democratic candidate exceeded one percent.
"With 55 per cent of the Democrats we surveyed behind her, Hillary Clinton is in solid position to win the nomination with Bernie Sanders and Joe Biden trailing well behind," Tim Malloy, the assistant director of the poll, told CBS News.
Early-voting state polls also reflect Clinton's enduring strength, though the gap is a bit narrower: A Quinnipiac survey last month found Clinton at 52 and Sanders at 33 in Iowa. And an NBC/Marist poll released earlier this month found Clinton at 42 and Sanders at 32 in New Hampshire.
For all the progress he's made in polls, Sanders still has a long way to go if he hopes to surpass Clinton. His campaign believes a victory in one of the early states could snowball into more momentum as the primary progresses.
"We're focused on building out after Iowa and New Hampshire," Devine explained. "When there's a surprising victory in an early state by a longshot opponent, the tables can turn very quickly."
Sanders has been no slouch in terms of fundraising, but his second-quarter haul was still dwarfed by the Clinton money machine.
Between April and June this year, Sanders' campaign announced earlier this month it had taken in $15 million - a total secured largely through small-dollar donations collected online and at Sanders rallies.
It was an impressive number, but it didn't hold a candle to the $45 million Clinton's campaign raised during the same period. And that's not even including the array of Clinton-friendly outside groups that are expected to spend millions more boosting the former secretary of state through the primary and general.
Sanders' team insists it's not trying to out-raise Clinton - only to raise enough to keep their candidate competitive until voter enthusiasm can help tilt the balance of the race in their favor.
"I think the support for Bernie is growing," Devine told CBS News. "We're seeing that manifested in the contributions which continue to come in. Low dollar contributions have given us the resources we need to run an election."
"By the time we get into late fall and early winter, I think we'll have a structure in place to build on an early success," Devine predicted.
Team Sanders has also emphasized their candidate's reluctance to stroke donors and accept help from outside groups like super PACs. Those decisions may hurt his bottom line, they concede, but they have the political benefit of showing voters that Sanders can't be bought - that he's more concerned about grassroots support than checks from big donors.
That may be an attractive political argument, but you can't fund a presidential campaign on sanctimony alone. You need an organization, television ads, and boots on the ground in key states - preferably more of each than your opponent. Those things cost money, and right now, Clinton has a lot more of it than Sanders.
It's nearly impossible for a Democrat to win an election without significant support among black voters, and there's evidence Sanders may have a tough time earning that support.
Netroots Nation, a gathering of liberal activists, was disrupted earlier this month by protesters from a group called Black LivesMatter, who demanded to know what Democratic candidates would do to combat institutionalized racism.
Sanders, one of two candidates who attended the gathering, grew frustrated as he tried to answer the protesters, declaring, "I spent 50 years of my life fighting for civil rights and for dignity. But if you don't want me to be here, that's OK. I don't want to outscream people."He then offered his standard message about economic empowerment and income inequality, pointing out (correctly) that black and Latino Americans are disproportionately affected by low wages and unemployment.Many activists, though, said that was beside the point - a welcome statement of truth that nonetheless failed to address their concerns about non-economic forms of injustice. They took to Twitter with the hashtag #Berniesoblack to mock Sanders' tone-deaf response.Sanders has since tried to make amends, speaking at length about criminal justice reform and pointing out his own personal investment in the civil rights battles of the past half century.
"I think we have a very powerful story to tell about Bernie Sanders - his civil rights activism, his record on issues of concern to the African American community," Devine explained. "What we've gotta do is start at the beginning."
He has quite a bit of ground to make up among black voters, according to survey data. Only 3 percent of Black voters voiced support for Sanders in Quinnipiac's poll, while 73 percent threw their lot in with Clinton - a much wider gap than among the electorate as a whole.
Among Latino voters, too, Sanders is facing an uphill battle, thanks to Clinton's longstanding support in the community and his own history on immigration issues.
"Hillary Clinton is an established brand with Latino voters. It was Latino voters who kept her candidacy alive in 2008 until the very end," said Arturo Vargas, the executive director of the National Association of Latino Elected Officials (NALEO), in an interview with CBS News. "She has the advantage of a strong base to build from, and it's institutionalized, in that most of the elected officials and leaders are already there."
Sanders, by contrast, is an "unknown quantity," Vargas added. "Being from Vermont, there is no Latino base that he could naturally cultivate in his home state. When he was announcing his candidacy, there were lots of questions about his positions on what we would brand as Latino issues."
Still, Vargas allowed that Sanders has made some inroads: "He spoke at the NALEO conference last month, and I would say he left the conference having surprised our constituency. He was interrupted by applause more than Clinton was."
One episode that continues to dog Sanders among some Latinos is his role in scuttling a comprehensive immigration reform bill in 2007. He voted against the bill because of concerns that it would flood the U.S. labor market with cheap labor and squeeze American workers out of their jobs.
Immigration reform advocates haven't forgotten.
"I wasn't happy when he voted against the bill and I wasn't happy we lost. It hurt," Frank Sharry, the head of America's Voice, told Politico last month. "In retrospect, we realized that the only way we can proceed is that progressive forces are united behind the bill."
Illinois Rep. Luis Gutierrez, one of the most outspoken immigration advocates in Congress, turned the criticism up a notch during an interview with Larry King last month, saying Sanders has been conspicuously silent on immigration policy.
"I don't know if he likes immigrants, because he doesn't seem to talk about immigrants," said Gutierrez, who has endorsed Clinton's bid.Devine suggested Sanders' past on immigration won't hurt him among Latinos after they get a fuller look at his record.
"The fact that Bernie is so strong with organized labor, and doesn't want the GOP scenario of bringing as many people in to work low wage jobs as possible - the fact that he stands against that, no, I don't think that will hurt him ultimately with Latinos," he said. "I think they'll see someone who's on their side.
Still, Devine conceded, "We've got a ways to go. They don't know him the way they know Hillary."
Perhaps the most damning knock against Sanders is that he'd have a tough time winning a general election.
Many in the Democratic establishment say they agree with Sanders on the issues. They like his message on economic mobility, they welcome his advocacy on wages and trade, they appreciate his candor and his unvarnished style. But they're voting for Clinton, because they're certain Sanders would get creamed by Republicans on Election Day - and they worry he might drag the party down with him.
In a recent essay for Politico Magazine entitled "Why progressives shouldn't support Bernie," former Massachusetts Rep. Barney Frank warned Democrats, "Wishful thinking is no way to win the presidency."
"There is not only no chance -- perhaps regrettably -- for Sanders to win a national election. A long primary campaign will only erode the benefit Democrats are now poised to reap from the Republicans' free-for-all," argued Frank, who is himself something of a progressive icon. "I wish we lived in a country where the most relevant political dispute was over how far to the liberal side the electorate was prepared to go. Until we do -- and I will continue to work with Sanders and others to get us there -- spending our resources on an intraparty struggle rather than on working to defeat our very well-funded conservative opponents is self-indulgence, not effective political action."
There is some survey data that indicates Clinton would be a stronger general election contender than Sanders. In the latest Quinnipiac Poll, for example, Clinton is neck-and-neck with GOP challengers like Jeb Bush and Scott Walker in hypothetical matchups. Sanders trails both Republicans narrowly.
And Clinton has thus far completely dominated the race for endorsements from Democratic officeholders -- a strong sign of support among the party establishment. At least 30 Democratic senators and at least 80 Democratic House members have already thrown their support behind Clinton, representing well over half of the party's congressional delegation. And at least seven sitting Democratic governors have endorsed Clinton as well.
Sanders' totals: zero, zero, and zero, respectively.
Say this for Team Sanders, though: they at least know they have a lot of convincing to do if they're going to corral the party establishment behind Sanders' bid.
"In the end, if we're going to win this thing, it will be because we won these early states, and the last piece of the puzzle is convincing the party leaders and elected officials that Bernie will be a better standard bearer and turn out a better electorate for the party" than Clinton would, Devine said.