At a time when many national political figures are trying to figure out how America can diminish its presence in Iraq, Senator McCain is again bucking the trend.

“Roughly, you need another 20,000 troops in Iraq,” Mr. McCain said Friday during a visit to northern New Hampshire. “That means expanding the Army and Marine Corps by as much as 100,000 people. … It’s just not a set number.”

Mr. McCain’s comments were carried Friday evening by the Associated Press and on Saturday by the Union Leader of Manchester, N.H., but attracted little attention.

The Arizona senator, who is a leading contender for the Republican presidential nomination in 2008, speaks regularly about boosting the size of the active-duty military by 100,000 or more. However, Mr. McCain rarely recommends a specific number of additional troops to be sent to Iraq to quell the violence there. About a year ago, Mr. McCain urged a boost of 10,000 in the American troop levels in Iraq.

According to the Pentagon, about 141,000 uniformed American military personnel are in Iraq.

Political observers differed about the impact of Mr. McCain’s aggressive stance on his presidential bid, but there has been no rush to embrace his position.

Appearing yesterday on ABC’s “This Week,” the House majority leader, John Boehner, gave no direct answer when asked about Mr. McCain’s suggestion. “The president is listening to the commanders on the ground and we’re going to do everything we can to support the commanders on the ground, but winning is the only option,” Mr. Boehner said.

A Republican congressman from Connecticut who campaigned with Mr. McCain on Saturday, Christopher Shays, said he wanted to consult with the Pentagon before offering an opinion on the senator’s proposal, the AP reported.

A political analyst at the University of Virginia, Larry Sabato, said Mr. McCain’s approach would improve his standing with the Republican faithful. “It helps him enormously in the Republican Party,” Mr. Sabato said. “There are many Republicans, probably a majority, who want to see more troops sent if you really question them on it.”

Mr. Sabato said he doubted others in the GOP field would endorse Mr. McCain’s view, but it was still smart politically because of the doubts many conservatives harbor about him. “The Republican candidates who are more conservative have no fundamental problem with the base. McCain does. He needs to use every opportunity,” Mr. Sabato said.

A political science professor at Boston College, Alan Wolfe, said last week that Mr. McCain’s stance in favor of more troops was a political loser. “What McCain is doing now is suicidal,” Mr. Wolfe told the Boston Globe. “He wants to be admired as Mr. Integrity, but he’s hurting himself with many independent voters and many Republicans.”

Mr. McCain’s public talk of boosting the American military commitment to Iraq also runs counter to the political strategy recently advocated by one of his likely rivals for the Republican nomination, Majority Leader Frist.

“The challenge is to get Americans to focus on pocketbook issues, and not on the Iraq and terror issue,” Dr. Frist told the Concord Monitor last week. The Tennessee senator warned about Democrats “waving the white flag and surrendering,” but made clear that he views the Iraq issue as an albatross for Republicans.

During the 2004 presidential campaign, some Democrats urged their nominee, Senator Kerry of Massachusetts, to outflank President Bush by urging that more troops be sent to Iraq. In May of that year, Mr. Kerry called for increasing the American military’s active-duty force by 40,000, including 20,000 combat troops. He said some of those troops could replace reservists in Iraq, but was unclear at that time about whether he wanted to increase the overall size of the force there. By August 2004, Mr. Kerry was talking about “significant” cuts in troops in Iraq by 2008.

Speaking last week on ABC, Mr. Kerry called Mr. McCain’s plan “a fantasy.”

“Our own generals tell us the solution in Iraq is not military. If it’s not military, don’t talk as John McCain does, about putting more troops in,” Mr. Kerry said. “Talk about how you resolve the political and diplomatic dilemma and sectarian dilemma between Shia and Sunni and the region.”

One advocate for an aggressive response to the Islamist threat, Frank Gaffney of the Center for Security Policy, said yesterday that Mr. McCain’s approach was essentially unworkable. “We’d be hard pressed to put 20,000 more people on the ground,” Mr. Gaffney said. He said defense cuts in the 1990s left the military diminished. “War is a come-as-you-are party. We’re using about as much force as we can muster.”

In a separate development yesterday, Senator Biden, a Democrat of Delaware, delivered a sharp retort to Defense Secretary Rumsfeld’s comments Thursday telling Iraq war critics to “back off” and “relax.”

“Relax? Huh? While we’re getting killed, while 140,000 troops are there, while they have no plan for success and he’s telling us to relax,” Mr. Biden said on CNN. “Come on.”