WASHINGTON— Six-term Indiana Sen. Richard Lugar was routed by the right flank of his own Republican Party on Tuesday, part of a show of conservative enthusiasm and strength six months before the nation chooses between Democratic President Barack Obama and GOP rival Mitt Romney.

Romney swept three Republican primaries, moving ever closer to sealing his nomination in an otherwise sharply polarized environment.

“We are experiencing deep political divisions in our society right now. These divisions have stalemated progress in critical areas,” Lugar, 80, a Capitol Hill diplomat and deal-maker, said as he conceded to the tea party-backed GOP opponent who ended his nearly four-decade career in the Senate.

The highly charged and hard-fought contests overshadowed Romney’s continued progress toward the GOP presidential nomination.

The former Massachusetts governor won the Republican presidential primaries in Indiana, North Carolina and West Virginia — states in which he faced no serious opposition — drawing close to the 1,144 delegates he needs to clinch the nomination.

He won at least 59 delegates, with 37 still undecided. He had 915 delegates, 229 shy of what he needs to become the formal Republican presidential nominee.

The results of Tuesday’s far-flung voting gave clues about the state of the electorate — and illustrated the political minefields facing both Republican and Democratic candidates — with the presidential contest well under way.

The results were a warning to incumbents. They also highlighted tea party enthusiasm.

And, in one state at least, they indicated that wedge issues are still a force even with an electorate focused on economic concerns.

Also, there was an indication of just how unpopular Obama is in some parts of the country.

A man in prison in Texas was getting nearly 4 out of 10 votes in West Virginia’s Democratic presidential primary against Obama, who faces no serious primary challenger. The inmate, Keith Judd, is serving time at the Beaumont Federal Correctional Institution in Texas for making threats at the University of New Mexico in 1999.

Lugar’s foe, state Treasurer Richard Mourdock, had painted the Republican senator as too moderate for the conservative state.

Within minutes of Lugar’s loss, Democrats were already painting Mourdock as too extreme for the state.He will face Democratic Rep. Joe Donnelly in November.

Republicans need to gain four seats to take control of the U.S. Senate, and a Lugar loss “gives Democrats a pickup opportunity,” Sen. Charles Schumer, D-N.Y., said.

Earlier in the day, Lugar, 80, made clear he would stand by Tuesday’s outcome, ruling out running as an independent.

With 98 percent of precincts reporting, Lugar had just under 40 percent of the vote to Mourdock’s just over 60 percent.

Also Tuesday, Democrats overwhelmingly picked Milwaukee Mayor Tom Barrett to challenge Republican Wisconsin Gov. Scott Walker in a June 5 recall election. The primary outcome set up a rematch; Barrett lost to Walker in 2010.Barrett was one of four Democrats on the ballot Tuesday.

Union rights are dominating the recall fight.Walker effectively ended collective bargaining rights for most state workers, and since then has emerged as a national conservative hero.

---- Former Pennsylvania Sen. Rick Santorum, who gave Romney a tepid endorsement Monday night via email, and former House Speaker Newt Gingrich have dropped out of the race. Texas Rep. Ron Paul is still contesting the nomination, but he lags far behind in the delegate count. ---- LoBianco reported from Indianapolis. Associated Press writer Donna Cassata in Washington contributed to this report.