Tea party set to topple Sen. Richard Lugar. Could he try third-party run?

Indiana voters appear close to dealing long-time Sen. Richard Lugar (R) a major setback in Tuesday's Republican primary. His tea party-backed challenger, who says Senator Lugar isn't conservative enough and is out of touch with his home state, holds a sizeable lead, according to polls.

If dealt a primary loss, could Lugar mount a viable third-party run as an independent?

Sen. Joe Lieberman (I) of Connecticut, ejected in the 2006 Democratic primary, retained his seat by running under a new party flag, "Connecticut for Lieberman." Sen. Lisa Murkowski (R) of Alaska, after losing a primary in 2010, held her seat by winning as a write-in candidate.

Like them, Lugar has plenty of name recognition and a reserve of goodwill among voters in his home state. But several political analysts say they expect the Republican primary to determine the fate of Lugar's six-term Senate career, suggesting he's unlikely to run as a third-party candidate.

"I would be very surprised if he would do that," says Gary Crawley, a political scientist at Ball State University in Muncie, Ind.

Lugar's challenges would be fundraising and the probability that he would hurt his own party in the process. The effort might divide the state's Republican vote, opening the door to Democrats gaining a new seat in the Senate. In the process, some political analysts say that dividing Republican ranks could even allow President Obama to carry the state, which would aid the president's reelection chances considerably.

Pollsters generally expect Indiana to go Republican in this fall's presidential race, although Mr. Obama won the state in 2008.

"I don't think that Lugar would want to split the party," says Brian Vargus, a political scientist at Indiana University in Indianapolis. "The coalition between social and economic conservatives in Indiana is very, very fragile."

For now, the big question is whether Lugar will win or lose the primary.

A Howey/DePauw poll released last week showed challenger Richard Mourdock leading among likely voters, 48 to 38 percent. In late March, the poll showed 42 percent supporting Lugar and 35 percent for Mr. Mourdock, currently the Indiana state treasurer.

Mourdock has "done a pretty good job of saying Lugar is out of touch," says Mr. Crawley.

The challenger has emphasized Lugar's out-of-state residency, his age, and his long tenure – Lugar entered the Senate in 1977 – with a message of "it's time" for someone new. The conservative Club for Growth has given Mourdock its financial backing, and Lugar has found himself labeled the Obama administration's favorite Republican.

Among his actions while serving as treasurer (since 2006), Mourdock challenged the Obama administration's bailout of Chrysler Corp. as an unfair deal for Indiana retirees who saw Chrysler bond holdings sharply devalued in bankruptcy court.

Despite the poll results, what matters Tuesday will be who shows up to vote. Turnout could be light, judging by the relatively slow pace of absentee ballots. The state's Republican Party establishment is trying to rally support for Lugar, since the Senate seat appears safe if he's the nominee. But Mourdock's rise in poll suggests the challenger may have the needed momentum to win.

If Mourdock is the nominee, the fall race looks like a close battle against Rep. Joe Donnelly, the Democratic contender.