John Bolton may be on his way out as ambassador to the United Nations, but he may yet live on as an issue in the 2008 presidential campaign.

Mayor Bloomberg yesterday came to John Bolton’s defense, calling the movement to block the U.N. ambassador’s Senate confirmation a “cheap political stunt on the part of a handful of people.”

Mr. Bloomberg called the holdup of Mr. Bolton’s nomination, which led the envoy to resign Monday, a “disgrace” and “an outrage,” and said “countries like America and Israel will suffer because they won’t have John Bolton there.”

“John Bolton was a guy that was standing up and trying to change the United Nations in a ways that would make it a lot more responsible,” Mr. Bloomberg told reporters before touring the city’s new emergency-operations bunker in Brooklyn. “Hopefully the president can find someone else with the same skills that will get through the Congress, but I think that it’s not what the Founding Fathers meant when they talked about advice and consent.”

While Mr. Bloomberg has publicly voiced support for Mr. Bolton before, yesterday’s comments were his most extensive and his most blunt. And for Mr. Bloomberg, a Republican who often doles out harsh criticism for his party, they underlined the independent streak that led him to back Senator Lieberman for re-election, to take on Congress on gun control, and to form alliances with lawmakers from both parties all over the country.

Since Mr. Bolton’s resignation was made public Monday, a number of possible 2008 presidential contenders other than Mr. Bloomberg have weighed in. On the Republican side, Senator McCain of Arizona, has called Mr. Bolton’s resignation a “deep disappointment.”

“His resignation today is less a commentary on Mr. Bolton than on the state of affairs in the U.S. Senate,” Mr. McCain said. He added that by blocking a full vote on the matter on the Senate floor Democrats on the Foreign Relations Committee “have deprived America of the right man at the right time at the UN.”

The communications director for Governor Romney of Massachusetts, Eric Fehrnstrom, said the governor was “deeply disappointed.”

Mr. Fehrnstrom said Mr. Romney, has a “great deal of respect for Ambassador Bolton and believes he was a strong force for reform.”

When asked whether the governor, who is a likely 2008 presidential candidate, agreed with Mr. Bloomberg’s comments, which were more blunt, Mr. Fehrnstrom said, “Our sentiment is basically the same.”

The 2004 Democratic presidential nominee, Senator Kerry of Massachusetts, in July called the U.N. envoy the “wrong man” and said he has “helped isolate the United States, made it harder to pursue our interests and failed to get results on our critical security issues.”

This week, Mr. Kerry, another possible candidate in 2008, said Mr. Bolton’s resignation “offers a chance to turn the page at a critical period.” “We need a United Nations ambassador who has the full support of Congress,” he said in a statement posted on his Web site.

Mr. Bolton’s resignation ended a political battle for the White House. Mr. Bush had made an end run around Congress and appointed Mr. Bolton while lawmakers were out of session last year.

The chances of a confirmation began to look increasingly grim last month when Senator Chafee, the outgoing Republican from Rhode Island and a member of the Senate Foreign Relations Committee, said he would not back Mr. Bolton, whose term is set to expire at the end of the month.

Senators Clinton and Schumer, who both voted to block Mr. Bolton’s nomination when it was before Congress for the first time in 2005, have remained largely out of the fray this time. Neither of their offices returned calls for comment yesterday.

In July, Mr. Schumer, speaking on CNN, said a Democratic filibuster was “unlikely,” and said he was considering backing Mr. Bolton this time around because of the envoy’s strong support of Israel.

“There’s a good part of Bolton. He’s been a staunch defender of Israel,” Mr. Schumer said. “There’s a bad part of Bolton. He seems to have a ‘go it alone’ attitude at a time when we need the nations of the world on our side.”

Mrs. Clinton has remained largely out of the public eye on Mr. Bolton’s renomination. Senator Obama, who has sparked a recent round of excitement with a suggestion that he may challenge Mrs. Clinton for the Democratic presidential nomination, has spoken out against Mr. Bolton.

In May 2005,Mr. Obama said that Mr. Bolton has sought to “sideline career intelligence analysts who did not agree with his policy views.”

“This is the core of the bipartisan objections to this nomination,” he said during a Senate debate, noting that he had supported other Bush nominees.

Opponents have painted Mr. Bolton as a conservative ideologue, while supporters say that he is shrewd asset who is helping to improve the floundering world body.

Mr. Bloomberg — who appointed his sister, Marjorie Tiven, as the city’s commissioner to the United Nations — said that Mr. Bolton is clearly capable and that elected leaders should not block his confirmation simply because they disagree with the president’s policies.