WASHINGTON — With social conservatives up in arms over the possibility that Senator McCain may tap a supporter of abortion rights, Senator Lieberman, as his running mate, one staunch McCain ally and abortion opponent says the Connecticut lawmaker is the perfect choice.

Rep. Peter King, a Long Island Republican, said social conservatives are making a mistake by opposing Mr. Lieberman, arguing that the 2004 Democratic vice presidential nominee could help deliver Mr. McCain the election in November. While ardent abortion foes have said the “pro-life” principle is too important to give up for the sake of political pragmatism, Mr. King turned the argument on its head, saying that electing an anti-abortion president in Mr. McCain outweighs the risk of a more conservative vice presidential pick that would ultimately lose to Senator Obama in November.

“They would be the ones morally responsible for electing a pro-choice president,” Mr. King said of Mr. Lieberman’s right-wing critics in an interview with The New York Sun yesterday.

His comments came as the Republican National Committee announced yesterday that Mr. Lieberman will address the Republican convention next month.

Mr. King has long been a booster of Mr. Lieberman, suggesting him for vice president earlier in the year. They have shared a conservative stance on national security and foreign policy, working closely on those issues; Mr. Lieberman, an independent who caucuses with the Democrats, is chairman of the Senate Homeland Security Committee, while Mr. King held that post in the House until last year.

Like Messrs. McCain and Lieberman, Mr. King has broken with his party’s base before, and in the Republican presidential primary, he backed a candidate who supported abortion rights, Mayor Giuliani.

Mr. McCain drew the ire of opponents of legalized abortion when he told the Weekly Standard last week that the support of abortion rights would not necessarily disqualify a former Pennsylvania governor, Tom Ridge, as a prospective running mate. And reports have spread this week that he also is considering Mr. Lieberman.

The news has led to angry warnings from social conservatives, and the talk radio host Rush Limbaugh said Mr. McCain would “destroy the Republican Party.”

“I understand the sincerity but I really believe it’s misguided, and I’m saying that as a person who has a 100% pro-life voting record,” Mr. King said.

Mr. McCain refused to offer any hints yesterday in an appearance on “The Laura Ingraham Show,” in which the host, Ms. Ingraham, urged him to select an anti-abortion running mate.

In addition to Mr. Lieberman, the RNC announced several other convention speakers, including Mr. Giuliani, who will deliver the convention’s keynote address. The roster of speakers also includes virtually all of the other candidates who sought the Republican nomination this year.