WASHINGTON (Reuters) - The landslide defeat of U.S. Senator Richard Lugar in Indiana sent an ominous message to Washington: unprecedented partisan gridlock in Congress likely will worsen next year and make difficult efforts to cut the record U.S. debt even tougher.
Tuesday's vote also delivered a punch to the gut of the Senate's "old guard," which for years has sought to restore the chamber's reputation as "the world's most deliberative body."
Widely hailed as an elder statesman, Lugar lost the Republican primary in his home state to a Tea Party-backed challenger, largely because he was seen as not conservative enough and too willing to compromise.
While politics has been long defined as the art of compromise, victor Richard Mourdock, who ridiculed Lugar's willingness to cut deals, made a prediction about next year.
"I don't think there's going to be a lot of successful compromise," Mourdock told CNN on Wednesday after beating Lugar, a 36-year veteran of the Senate, by double digits. Bipartisanship, Mourdock added, means Democrats voting for Republican initiatives.
The Indiana election result shook many of Lugar's colleagues on both sides of the political aisle who saw him as a giant on foreign policy and arms control.
"This is a tragedy," said Democratic Senator John Kerry, who heads the Senate Foreign Relations Committee where Lugar serves as the top Republican. "He will be missed."
Lugar's loss follows the defeat in primaries of two Democratic moderates by liberal challengers in the U.S. House of Representatives - and the resignations of three of Lugar's moderate Senate colleagues.
All had drawn fire from their parties' left or right wings, underscoring that lawmakers who move toward the middle could be committing political suicide.
"The gridlock and dysfunction is likely to intensify next year," said Greg Valliere of Potomac Research Group, a private firm that tracks Congress for investors.
"The partisans in both parties will become more powerful, so getting much done on deficits still looks like an uphill battle," Valliere added.
The Republican-led House and Democratic-led Senate have been at odds much of the past 18 months, failing to agree on any major deals to stimulate the economy and seeing limited success at curbing the growing, $15.6 trillion record U.S. debt.
This has frustrated voters, translating to record low approval ratings for Congress - at times dipping into single-digits - and an anti-incumbent mood as both parties head into the November 6 election campaigns.
"People are unhappy with the status quo and anyone who looks like a Washington insider is at risk," said Paul Sracic, a political science professor at Youngstown State University in Ohio.
"The ironic result is Washington is likely to become more dysfunctional, and the people more unhappy," Sracic said. "It is hard to see how this ends well."
Democrats hope Lugar's defeat will give them their first real chance of winning his seat in more than three decades and bolster their chances to retain control of the Senate, which they now hold, 53-47.
But Indiana has long been a Republican state and Mourdock, the state treasurer, is favored to win, at least at this point, said Jennifer Duffy of the nonpartisan Cook Political Report.
On Wednesday, however, Duffy moved Lugar's Senate seat from "solid Republican" to "lean Republican," reflecting the fact that Democrats are at least seen as having a chance.
Lugar, 80, was hurt by questions about his politics as well as about his residence, compounding complaints by some that he had simply been in the Senate for far too long.
After being sworn into the Senate in 1977, he sold his house in Indiana and moved to Washington, frequently returning to his home state. The arrangement became a huge liability for him against Mourdock.
"His residency turned what would have been a close race into a blowout, said Tom Davis, a former moderate Republican House member. "This is a classic case of a guy who stayed too long."
Polarization on the Democratic side of the aisle is apparent as the once-influential "Blue Dog" caucus of fiscally conservative House Democrats is threatened with extinction.
Two Blue Dog congressmen from Pennsylvania, Jason Altmire and Tim Holden, were defeated last month in primaries by more liberal Democratic candidates. In part, they were punished by voters - and labor unions - for opposing Obama's healthcare overhaul law in 2010.
They also suffered from the once-a-decade process of redrawing congressional districts to reflect population shifts. Democratic districts have been combined in some states, forcing runoffs between incumbents, while in other cases, conservative areas have been carved away and added to Republican districts.
This has made both Republican and Democratic districts more concentrated, making centrist candidates less appealing to their constituents.
In the end, Indiana primary voters decided that Lugar was out of touch with them, said Senator Jerry Moran, a Tea Party-favorite from Kansas. Moran argued that the Tea Party, which boosted Republican clout in Congress in the 2010 elections, reflected mainstream desires.
"The Tea Party is everyday folks concerned about the size and scope of government. It's been accused of being extreme or radical," Moran said. "But since when did wanting Congress to live within its means become extreme or radical."
Democrats counter that it is extreme to rein in budget deficits by cutting social programs while allowing tax breaks for the rich to continue or even expand.
Lugar's more conservative Republican Senate colleague from Indiana, Dan Coats, said, "There is a restless and dissatisfied public out there. They want change. They aren't sure about what kind of change. But they want change."
Lugar said in a statement after his defeat, "If Mr. Mourdock is elected, I want him to be a good senator. But that will require him to revise his stated goal of bringing more partisanship to Washington."
Editing by Cynthia Osterman