When anti-tax crusader Grover Norquist visited the Indiana Statehouse last week, he made a public plea for U.S. Sen. Richard Lugar to sign his anti-tax pledge.

But he might not be able to persuade the veteran senator to get on board.

Lugar is the only Republican in the state's Congressional delegation who hasn't signed Norquist's pledge, which requires the signer to "oppose and vote against any and all efforts to increase taxes." The pledge is popular in tea party circles, and for Lugar, who faces a tough primary challenge from State Treasurer Richard Mourdock, a tea party favorite, signing it might seem to make sense.

But Lugar says he won't sign any political pledges because they tie lawmakers' hands. He told a group at a Kiwanis Club event in Indianapolis last month that the new generation of Washington lawmakers has made so many ironclad guarantees that negotiating a compromise on issues like raising the nation's debt ceiling has become extremely difficult.

"A good number of members said they are not in a position to vote for any plan," Lugar said before the debt ceiling talks intensified Sunday.

Pledges, many of them advanced from the right, are proliferating as candidates get closer to 2012. Norquist's Taxpayer Protection Pledge is one of the oldest and has arguably the broadest reach in the nation. Since Norquist began selling it to lawmakers in 1986, the pledge has gathered signatures of more than 1,000 lawmakers.

The pledge found itself at the center of the national debate over the debt ceiling because of its broad and near-absolute influence on the many lawmakers who have signed it.

Norquist, president of Americans for Tax Reform, said he understands Lugar's concerns.

"You don't want to take the pledge unless you know you can keep it," he said.

But the discomfort with the pledge might go deeper, because it could box candidates in.

"It's not a pledge to me, it's not a pledge to Americans for Tax Reform, it's a pledge to the citizens of the United States," Norquist said. "What happens is the people who break the pledge have to go back to the people of their electorate and say, 'I know I told you I wouldn't (raise taxes) and I did.'"

Norquist's success in getting local, state and federal lawmakers to sign his anti-tax pledge helped fuel a national movement of interest groups drafting pledges to lock in politicians' fealty. That fealty, of course, is to the idea as much as the group pushing the idea.

Mourdock, who is challenging Lugar in the May 2012 Republican primary, has signed onto four political pledges thus far, campaign spokesman Chris Conner said.

Those include Norquist's pledge, the Cut, Cap and Balance Pledge, the Contract from America and a pledge to support the Parental Rights Amendment.

The Cut, Cap and Balance Pledge supports Republican calls for a balanced budget amendment to the Constitution. The Contract from America is a sweeping charter that calls for everything from repealing the federal health care overhaul law to supporting revamped energy policies. The Parental Rights Amendment would make it easier to homeschool children.

Every Republican in Indiana's congressional delegation voted in favor of the Cut Cap and Balance Act a few weeks ago. But as of Friday, only one Hoosier congressman — Rep. Dan Burton — had signed a pledge to support the act.

Lawmakers like Lugar say such pledges can create political gridlock. But while Norquist's pledge sounds pretty definitive, the debate over the debt ceiling exposed some loopholes.

In an interview with The Washington Post, Norquist said signers of his pledge could vote for President Barack Obama's plans to close tax loopholes and end tax credits without violating the pledge. He later walked that statement back some under fire from conservative activists

Generally speaking, if there was no net increase in tax revenue, it was safe to vote for a tax measure, he said last week.

"You really look at common sense on this. "If people look at it and say, 'That's a tax increase,' it is. The tie goes to the taxpayer," he said.