WASHINGTON — The McCain campaign is gearing up to criticize Senator Obama for his past associations with the Reverend Jeremiah Wright and a former Weather Underground operative, William Ayers, in the home stretch of the presidential race.

The McCain campaign, according to one aide, decided it would play the Wright and Ayers cards after Mr. Obama’s campaign ran ads linking Senator McCain to a talk radio host, Rush Limbaugh. “Our position is we are no longer going to feel constrained to avoid his very real associations in contrast to the very fictional associations he has imputed to John McCain in this campaign,” this aide said.

The Wall Street Journal on September 19 quoted one of Mr. McCain’s top aides, Mark Salter, as saying the campaign was “tired of catching spears.” He also said, “They played it one way, we played it another way. Now we’re both going to play it the same way.”

Last night, the campaign also denounced as “shameless and dishonorable” an Obama campaign ad that attacked Mr. McCain for not using a computer. Senator Biden, Mr. Obama’s own running mate, called the ad “terrible” and said, “if I’d had anything to do with it, we would have never done it.” Mr. McCain’s arms don’t function well, impeding computer use, because the Vietnamese communists broke them while torturing Mr. McCain and then denied him proper medical treatment while he was being held a prisoner in a war Mr. Biden avoided serving in by virtue of student and medical exemptions.

Mr. Biden’s press secretary late last evening sent out a statement rescinding his initial comment.

Any decision to run ads that feature Mr. Obama’s former spiritual adviser, Rev. Wright, is bound to attract jeers from the press. Already, Time magazine’s Karen Tumulty has written that an ad featuring a former Fannie Mae chairman, Franklin Raines, was racist. Mr. Raines, like Mr. Obama, is an African American. An ad that pointed out Mr. Obama’s longtime association with Rev. Wright, who emphatically hollered in one videotaped sermon: “God Damn America,” will likely draw responses from Democrats claiming that Mr. McCain is appealing to the racial fears of Americans.

A spokesman for the Obama campaign said their side sees the ads coming. “Of course the McCain campaign is going to run these ridiculous, gutter ads,” Tommy Vietor said. “Their strategy is to change the subject from the fact that John McCain put seven top Washington lobbyists in charge of his campaign and is so out of touch that he said that the fundamentals of the economy are strong on the day of a financial crisis.”

The McCain campaign’s push will likely not be limited to Senator Obama’s ex-pastor, whom the Chicago lawmaker criticized in the spring after having earlier said he would not disown him. Another association will be William Ayers, the former agent for the Weather Underground, a violent left wing group that exploded defense labs and other government buildings in the late 1960s and 1970s. Mr. Ayers, in an interview with the New York Times published on September 11, 2001, said he regretted not doing more when he was in the group. Senator Obama attended a fundraiser at the home of Mr. Ayers and also served on the board of the Woods Foundation with him in Chicago.

Mr. McCain’s chief strategist, Steve Schmidt, on a conference call with reporters Monday said that Mr. Obama has not been as forthcoming as he should be about his relationship with Mr. Ayers. “What we know for sure and is beyond debate and argumentation is this: Senator Obama said that William Ayers is a guy he lives in his neighborhood. We know that that is a disingenuous and untruthful answer. … There is a greater relationship than that of a guy who lives in my neighborhood between the two of them,” he said.

Along the lines of Mr. Obama’s past associations, the McCain campaign also launched at ad today titled “Chicago Machine,” that links the senator to a convicted felon, Tony Rezko, who raised money for the Obama campaign and Mayor Daley of Chicago.

A scholar at the American Enterprise Institute, Norman Ornstein, said, “It is an absolute hoot if they are suggesting we would have behaved if only he had agreed to town meetings, if only he had not run that ad.” Mr. Ornstein said the McCain and Obama campaigns do not need excuses to run negative ads or ads linking the candidate to unsavory past associates. “Neither candidate will stand on principles of etiquette if it reduces the chances of winning an election,” he said.

Mr. Ornstein mused that the Obama campaign may hit back by linking Mr. McCain to the Keating Five, a ring of senators caught up in the last major banking scandal in the late 1980s involving the collapse of savings and loans banks. “We could see a significant number of ads linking McCain to Charles Keating and McCain’s relationship with him,” he said. Mr. McCain has for many years protested his innocence in the affair, claiming he was dragged into the Ethics Committee investigation unfairly.

If the McCain campaign needs backup for insisting that the Ayers and Wright issues are fair game, however, it can cite Senator Clinton, who used them against Mr. Obama in the Democratic primary with some success.