(CBS News) How does a senator once described as "the George Washington of modern Indiana" find himself so unpopular he might get kicked out of office?
That's the question Republican Sen. Richard Lugar of Indiana is asking right about now as he faces the political fight of his life against state Treasurer Richard Mourdock in today's primary.
The longest-serving senator in Indiana's history, Lugar blames his weakened standing on the influence of money in modern politics.
"Thank goodness the founder of our country did not face millions of dollars of negative advertising," he told CBS affiliate WISH-TV last week.
First elected to the Senate in 1976, the 80-year-old former Indianapolis mayor became a prime target for conservative groups this year seeking to extend the Tea Party's influence in Congress and purge the Republican party of its moderates. They argue the senator simply doesn't represent his constituents anymore.
Lugar has indeed faced an onslaught of negative advertising in his re-election bid. Third party groups have spent $4.5 million on the race so far, according to the Center Public Integrity -- that's more than they've spent on any other congressional race this season, and about two-thirds of that cash is working against Lugar.
In at least one very important way, Lugar is more of a Washingtonian now than a Hoosier: The senator has lived in the suburbs surrounding Washington since 1977, and his residency became a campaign issue in this year's primary. Still, it may have taken national groups intervening in the state race to get Indiana voters to pay attention to Lugar's disconnect from the state.
Another victim of the Tea Party?
Polls show he is in serious trouble, withMourdock.
The senator, however, kept his chin up on Friday, telling WISH-TV that he could win if his campaign managed to turn around five voters per precinct. "It's very important Hoosiers take back our primary election from the outside world," he said.
Mourdock, a 60-year-old conservative who has served in Indiana politics since the mid-1990s, has essentially made the same case -- charging that it's Lugar who's part of the outside world.
The 30-second spot tells voters that Lugar has been called "Obama's favorite Republican." That label, said Margaret Ferguson, a political science professor at Indiana University, is the "kiss of death."
"And it's not as if he's a liberal," Ferguson said of Lugar to Hotsheet. "Being somebody who does a good job of working across the aisle.. that's really anathema right now."
When Lugar first ran for the Senate, in 1974, he lost in part because he was known as President Richard Nixon's favorite mayor and considered too Republican.
But even before Mourdock entered the primary, more than 70 Indiana Tea Party groups signed a proclamation vowing to support any challenger to run against Lugar.
The perfect PAC target
The Tea Party antipathy towards Lugar made him a perfect target for a more serious threat: Third party spending.
"Two months ago I rejected any intimation that Lugar would lose -- usually longtime incumbents don't just up and lose," Ferguson said. "This seems to be coming straight out of nowhere -- but the super PACs didn't really exist until this round."
Outside groups have spent more than $1.3 million supporting Mourdock as well as more than $1.6 million in opposition to Lugar. Some groups jumping into the fray include the National Rifle Association and FreedomWorks. The biggest player in the race has been the super PAC Club for Growth Action, spending more than $1.4 million.
Barney Keller, a spokesman for the Club for Growth, the Washington-based organization which advocates for lower taxes, said his organization's PAC "believes that there is a big difference between Sen. Lugar's record of support for bailouts, tax increases and record levels of debt and Richard Mourdock's opposition to tax increases, bailouts and records level of debt."
The Howey/ DePauw poll shows that voters have turned away from Lugar in just the past month -- while Mourdock is now up 10 points, he trailed Lugar by seven points in late March. Keller acknowledged the role his organization has played in shaping public opinion.
"Once Hoosier Republicans were presented simple facts about Sen. Lugar's record, combined with the vitriolic and nasty negative campaign ads that Sen. Lugar ran, they increasingly decided that it was time for principled leadership in the United States Senate," he said.
His attacks, however, may have come too late. Lugar still had $1.4 million in the bank as of April 18, the Indianapolis Star reported -- funds Lugar could've used earlier to fight back.
"We finally decided we were going to have to respond," Lugar said Friday. "After you take millions of dollars worth of hits, day in and day out, somebody ought to say Mr. Mourdock is unqualified to handle the complex problems of our world today."
Not a Hoosier
At the end of the day, Lugar simply "hasn't run a particularly good campaign," Ferguson said. "He was vulnerable to a challenge, and Mourdock offered him one."
While the senator is smart and knowledgeable, particularly when it comes to foreign policy, Ferguson said, "The fact is, he's been in Washington a lot more than he's been here... He doesn't have a house here, he doesn't even have a pretense of having a house here."
Residency issues have plagued longtime senators from both parties -- former Democratic Sen. Evan Bayh of Indiana came under scrutiny for listing a $60,000 Indiana condo as his official residence, even though he resided in a mansion in the Washington suburbs.
Lugar, though, doesn't even have a condo. In March, a local election board switch his voter registration to a family farm in Marion County, Indiana.in his home precinct. The senator resolved that issue pretty simply by agreeing to
But before he resolved the issue, Lugar admitted that the address listed on his Indiana driver's license was the address of the house he sold in 1977.
"The residency issue certainly has played a part in driving the narrative that Sen. Lugar is simply out of touch with Hoosiers," Keller said. Still, the Club for Growth spokesman added, the residency issue was simply symbolic of Lugar's larger issues. "The way that he is out of touch is his repeated votes for liberal policies that have bankrupted America."
Mourdock attacked Lugar's absence from the state from the very beginning: When he officially launched his campaign in February 2011, Mourdock released a list of nearly three quarters of Indiana's Republican County Chairmen who were publicly supporting his campaign.
The release announcing his campaign read, "Treasurer Mourdock noted that 'dozens and dozens of times' when he spoke to county chairmen about Senator Lugar, the response was effectively, 'Dick Lugar? I haven't seen him in years!""