Anti-tax evangelist Grover Norquist, one of Washington's most influential figures, is facing an apparent erosion of his power as leading Republicans begin opting out of pledges to his cause.

Norquist has amassed considerable clout over the last couple of decades by managing to get hundreds of Republicans in elective office to sign a controversial pledge vowing never to vote for a tax increase.

But there was growing feeling Sunday that the anti-tax crusader and his pledge were quickly becoming irrelevant as several party bigwigs said they would abandon the vow and analysts openly questioned his continued relevance.

"Grover Norquist is an impediment to good governing," Republican political strategist Matthew Dowd told ABC television's "This Week" program.

"The only good thing about Grover Norquist is, he's named after a character from 'Sesame Street,'" Dowd said.

"I think Grover Norquist's sell-by date has passed," said another longtime political observer, Joe Klein of Time Magazine.

Norquist, who heads the Americans for Tax Reform group, began collecting signatories to his pledge more than 20 years ago, gathering the names of politicians no less powerful than Mitt Romney, the recently-vanquished Republican presidential candidate.

Signatories to Norquist's "Taxpayer Protection Pledge" agreed to "oppose any and all efforts to increase the marginal income tax rates for individuals and/or businesses."

They also promised to "oppose any net reduction or elimination of deductions and credits, unless matched dollar for dollar by further reducing tax rates."

A longtime Washington player, Norquist is a Harvard MBA and trained economist whose rock-solid Republican credentials include membership on the board of the National Rifle Association (NRA) and the American Conservative Union.

He founded Americans for Tax Reform in 1985, and the group's website says that in the current legislature there are 238 House members and 41 senators who have taken the pledge, as well as 13 governors and 1,244 state legislators.

Any Republican lawmaker who breaks the no-taxes vow faces the opprobrium of their party and a probable primary challenge from a more hardline opponent who can be counted on to toe the party line.

But prominent Republican Senator Saxby Chambliss said last week that even a possible future election challenge was not enough to convince him to stick to his promise.

"I care more about my country than I do about a 20-year-old pledge," Chambliss told a Georgia television station last week.

As far as a primary challenge goes, he said, "I don't worry about that because I care too much about my country. I care a lot more about it than I do Grover Norquist."

Norquist's influence appears to have diminished quickly following the November 6 vote that re-elected Barack Obama and gave the president greater authority in talks to find measures to reduce America's ballooning debt.

Amid a growing consensus that it will take a combination of spending cuts and more revenue to rein in the deficit, the Republican leadership appears ready to jettison what had once seemed an iron-clad no-tax-hike promise.

"I will violate the pledge, long story short, for the good of the country," senior Republican Senator Lindsey Graham told "Fox News Sunday."

Republicans are only reconsidering their stance on taxes because a poison pill law -- designed to force action to rein in the debt -- will see a potentially catastrophic combination of tax hikes and spending cuts come into force if no deal is reached by the year-end.

Another prominent Republican to openly break with Norquist on Sunday was leading House representative Peter King.

One cannot be held to "a pledge you signed 20 years ago, 18 years ago," the New York lawmaker said on NBC's "Meet the Press" program.

"For instance, if I were in Congress in 1941, I would have signed a declaration of war against Japan. I'm not going to attack Japan today," he said.

"The world has changed," said King, "and the economic situation is different."