If Bernie Sanders' campaign has its way, Republicans might not be the only ones facing a contested convention this summer.
Sanders' top strategist, Tad Devine, predicted Monday that neither candidate will reach the 2,383 delegates necessary to win the Democratic nomination outright. "It is clear now that neither Hillary Clinton nor Bernie Sanders is going to go to the convention with a majority of pledged delegates," he said.
Coming off a trio of victories in caucus states last Saturday--Hawaii, Alaska and Washington--Sanders' team argued that he now has the momentum going into toward the rest of the calendar.
But while the math for Sanders isn't impossible, it's certainly not easy. According to CBS News estimates, Sanders would need to win two-thirds of the remaining pledged delegates and superdelegates in order to clinch the nomination -- whereas Clinton needs to win just a third of the remaining delegates in order to win the nomination outright.
"Sanders' path via the delegate math is possible but not all that probable," said Josh Putnam, a professor at the University of Georgia who tracks delegates on his website Frontloading HQ. "He would basically have to replicate Saturday's results across the remainder of contests. And those contests include a limited number of caucuses and a number of closed contests. That combination has not been a recipe for success for Sanders to this point in the race."
Meanwhile, the word you hear most often from the Clinton campaign when it comes to her delegate lead is this: insurmountable. On a responding press call, Clinton chief strategist Joel Benenson said the campaign expects to have things effectively wrapped up toward the end of April, by which point he argued the math doesn't add up for Sanders.
"The truth is, after April 26, there just simply is not enough real estate left for Senator Sanders to close the commanding lead that we've built," Benenson said. "We expect to come out of that day with a pledged and total delegate lead that will make clear who the nominee will be and that it will be Hillary Clinton."
Here are some reasons Sanders' path is tougher than his team suggests:
Devine told reporters Monday that Sanders has, since Nevada's caucuses, pursued a "state win" strategy, a move that depends more on winning states outright to get momentum than it does on racking up delegate numbers. But the margins matter a lot here, given the size of the deficit Sanders needs to make up.
Because Democrats' delegates are allocated proportionally throughout the entire primary season, just winning some of these states won't be enough: Sanders needs to win by massive margins, the same kind of margins he won by in the caucus states last Saturday. His team pointed out that he received a massive share of the vote in all three contests last weekend: in Alaska, he won by 64 points, in Washington by 46 points and in Hawaii by 40 points.
"You'd have to really win by a huge margin in places like Pennsylvania, New Jersey, New York, California," said Matt Seyfang, who has worked on delegate strategy for past Democratic presidential campaigns. "The margin would have to be absolutely massive."
But winning by big double-digit margins in a massive primary state like California or New York is far more difficult than winning by large margins in caucus states, where turnout is much lower. Thus far, Sanders' biggest margin of victory in a primary state, versus a caucus state, was about 10 percentage points in Oklahoma on March 1. And though Clinton had some wide margins of victory in a handful of primaries, especially those in the South -- she won Alabama by almost 60 points, for example -- most of the margins in primary states have been considerably closer.
Team Sanders noted Monday that there are still plenty of states friendly to Sanders on the map, naming New York and California as potential big opportunities for the Vermont senator.
But the places he has done best thus far have been in caucuses--and there are only two caucus states remaining, Wyoming (April 9) and North Dakota (June 7). In fact, with the exception of his upset victory in Michigan on March 8, Sanders has typically not done well in larger states. Clinton tends to pick up victories in those: take Ohio, Florida, and Arizona as recent examples.
Devine also said Clinton picked up most of her pledged delegate lead in states where the Sanders campaign didn't compete, which he named as Texas, Alabama, Virginia, Louisiana, Tennessee, Mississippi, Georgia and Arkansas.
But there's a bit of a problem with that argument. Sanders did contest at least some of those states: he campaigned in many of those states, put staff on the ground and even spent money on TV ads. In Texas, for example, he had seven offices around the state, the first of which opened in November for a March 1 primary; he also put a small amount of advertising into the state.
And if Sanders is going to catch up delegate-wise, he can't really afford to skip any states going forward.
Sanders' path to victory also includes something he thus far has not had great success with: winning over more superdelegates.
Jeff Weaver, Sanders' campaign manager, said Monday that the campaign is in "regular contact" with potential superdelegate backers, many of whom aren't ready to make their support public. (Still, "we don't have like 300 superdelegates waiting to endorse Bernie tomorrow," Devine quipped.)
The problem is that there really aren't that many uncommitted superdelegates left, at least compared to past years. Of the just over 700 total superdelegates, almost 500 have already backed a candidate (with Clinton leading among them 469 to 29).
As for flipping superdelegates, it's certainly possible--but even in 2008, only a few dozen superdelegates who'd committed to Clinton switched their allegiance to Obama while the contested primary was still going on. And that year, unlike in 2016, far more superdelegates remained uncommitted early on in the primary, so when they backed Obama they weren't actively switching candidates.
"To make a legitimate case to the superdelegates--pledged or not--Sanders is going to have to win somewhere (or a number of somewheres) where he is not expected to win: closed primaries," Putnam said.
As Clinton spokesman Brian Fallon noted on Twitter the night of the March 15 primaries, Clinton's delegate lead is already significantly bigger than President Obama's ever was during the 2008 race. Currently, the gap in pledged delegates is just over 250; in 2008, Obama's lead over Clinton hovered around 100 delegates.
Clinton stayed in the race until June, working hard to rack up delegates wherever possible -- and she even had some big victories, in places like Ohio, Texas and Pennsylvania. Still, those victories weren't enough to help her overtake Obama's delegate lead.
One thing Sanders does have going for him is money: he's far better funded than most primary challengers, and his campaign announced Monday that he'd raised $4 million since his caucus victories last Saturday. But that still doesn't make it easy for him to have the kind of blowout wins he'd need to really get ahead in the delegate count.
Seyfang said Sanders has already far exceeded expectations for his campaign, but that it doesn't change how hard the math is for him going forward.
"They have a lot to be proud of -- it really is a very impressive showing," he said. "I don't want to say it's impossible -- because it isn't -- but it's just really, really, really pushing the bounds of plausibility."