Six-term Indiana Sen. Richard G. Lugar lost a bitter challenge from the right flank of his own Republican Party on Tuesday night, his nearly four-decade career in the Senate ended by a tea party-backed GOP foe.
Mitt Romney, meanwhile, won GOP presidential primaries in Indiana, North Carolina and West Virginia, drawing close to the 1,144 delegates he needs to clinch the nomination.
"I have no regrets about running for re-election. Even if doing so can be a very daunting task," Lugar, 80, said as he conceded the primary election to State Treasurer Richard E. Mourdock.
Also Tuesday, Milwaukee Mayor Tom Barrett won the Democratic primary in Wisconsin's historic recall election, emerging from a field of three Democrats to face Republican Gov. Scott Walker next month. The recall, triggered by the collection of more than 900,000 petition signatures, was spurred by anger over Walker's proposal passed last year taking collective-bargaining rights from public workers.
The June 5 recall is one of the most closely watched elections in the nation outside of the presidential race.
Walker easily defeated Arthur Kohl-Riggs, a Walker opponent running as a Republican.
The outcomes of Tuesday's far-flung voting were certain to give clues about the state of the electorate -- and highlight the political minefields facing both Republican and Democratic candidates -- six months before the general election.
In the biggest race of the night, Lugar lost to Mourdock, who will face Democratic Rep. Joe Donnelly in the November general election. Republicans need to gain four seats to take control of the U.S. Senate, and a Lugar loss "gives Democrats a pickup opportunity," said Sen. Charles E. Schumer, D-N.Y.
Lugar ruled out running as an independent.
"This is it," he said with voting still under way.
Playing out in a conservative state, the race illustrated the electorate's animosity toward many incumbents and anyone with deep ties to Washington. Lugar was been in the Senate since 1977.
Lugar, who hasn't faced questions about his residency in decades, found himself on the defensive over whether he lived in Indiana or northern Virginia. Lugar also was cast as too moderate for the conservative GOP in Indiana, and he took heat for his work with Democrats on issues such as nuclear nonproliferation, underscoring deep polarization in the country as well as a split in the GOP between the establishment wing and the insurgent tea party.
In a statement, President Obama praised his former Senate colleague as someone "who was often willing to reach across the aisle and get things done."
On Capitol Hill, Republicans braced for Lugar's loss throughout the day.
"It says if you're an incumbent, you better not lose touch with home," said South Carolina Republican Sen. Lindsey O. Graham.
The race between Mourdock and Donnelly is expected to be hotly contested, with the potential to affect the White House contest.
Obama carried Indiana in 2008, partly because of his ties to the populous northwestern part of the state neighboring his hometown of Chicago. Democrats acknowledge that it will be difficult to win Indiana again this year. Still, the state could become more hospitable to Obama if the Democrats, believing they have a better chance with Lugar out of the race, spend heavily to compete against Mourdock.