After canceling campaign appearances with state Treasurer Bob Casey and other Democratic candidates across the country yesterday, Massachusetts Sen. John Kerry issued a statement of apology for a "botched joke'' that had been the target of increasing criticism from politicians of both parties.

"As a combat veteran, I want to make it clear to anyone in uniform and to their loved ones: my poorly stated joke at a rally was not about, and never intended to refer to any troop," the 2004 presidential candidate said in a statement released yesterday afternoon. "I sincerely regret that my words were misinterpreted to wrongly imply anything negative about those in uniform, and I personally apologize to any service member, family member or American who was offended."

The words reflected the evolving level of contrition that Mr. Kerry had displayed since Republicans began to attack the remarks he made Monday in California. Speaking to a group of students, he said that if they did not study hard enough, they would "get stuck in Iraq."

Mr. Kerry said the remark was an unsuccessful attempt at a joke at President Bush's expense, that he had meant to say that if you weren't intellectually curious, you would get "us" stuck in Iraq. But whatever its intent, the statement was manna from Massachusetts to a Republican Party reeling from ominous poll results a week before a crucial midterm election.

President Bush led a GOP chorus of denunciations. Speaking Tuesday at a campaign rally in Georgia, he drew boos with his mention of Mr. Kerry's name and said, "[His] suggestion that the men and women of our military are somehow uneducated is insulting, and it's shameful."

In an orchestrated barrage of criticisms, Vice President Dick Cheney assailed the 2004 Democratic presidential nominee while Republican House and Senate candidates across the nation echoed one another's news releases calling on Democratic rivals to repudiate Mr. Kerry and return any campaign funds he had helped raise for them.

As the controversy unfolded from Monday to yesterday, the calls for a Kerry apology took on an increasingly bipartisan color. Sen. Hillary Clinton, D-N.Y., said Kerry's statement was "inappropriate."

Rep. Harold Ford Jr., the Democratic Senate candidate in the closely watched Tennessee contest, was among members of his party who said Mr. Kerry should apologize. Jon Tester, the Democrats' Senate candidate in Montana, called the remark "poorly worded and plain stupid."

Mr. Kerry's staff said it was their decision to withdraw from a scheduled rally yesterday afternoon with Mr. Casey at the University of Pennsylvania. "We made a decision not to allow the Republican hate machine to use Democratic candidates as proxies in their distorted spin war," Kerry spokesman David Wade said in a statement.

Mr. Casey, who is seeking to unseat Republican Sen. Rick Santorum, said Tuesday that he had accepted Mr. Kerry's explanation that his "botched joke" had created the controversy. "That's what he said, and I take him at his word," Mr. Casey told a Philadelphia Inquirer reporter. "He served in combat. Last time I checked, the president and the vice president did not. The White House and the Santorum forces should get to work on dealing with the real problems in Iraq."

In appearances in Harrisburg and Philadelphia yesterday, Mr. Santorum castigated his rival for failing to speak out against Mr. Kerry.

At a news conference last night, the underdog Republican said of Mr. Casey, "... [H]e flunked the test of leadership, he flunked the test of standing up for our men and women [in uniform] when he had the opportunity to do that. He played partisan politics, and read from his talking points, just as he's done this entire campaign."

Casey spokesman Larry Smar dismissed the Republican's criticism. "After rubber-stamping the Bush policy in Iraq and saying [Defense Secretary] Don Rumsfeld is doing a, quote, fine job, Rick Santorum is in no position to lecture about leadership," he said.

The White House offered a chilly acceptance of Mr. Kerry's latest statement. "Senator Kerry's apology to the troops for his insulting comments came late, but it was the right thing to do,'' said Deputy Press Secretary Dana Perino.

The Massachusetts senator, who has made no secret of the fact that he is considering a renewal of his presidential ambitions in 2008, was at first defiant in the face of GOP criticisms of his Monday remark. "You know, education, if you make the most of it, you study hard, you do your homework and you make an effort to be smart, you can do well. If you don't, you get stuck in Iraq," he said then.

He and his office later said it was an ad lib that changed the meaning of an intended jibe at Mr. Bush.

Mr. Kerry's prepared remarks called for him to say, "Do you know where you end up if you don't study, if you aren't smart, if you're intellectually lazy? You end up getting us stuck in a war in Iraq. Just ask President Bush."

Mr. Kerry at first said he had no need to apologize to an administration that had so mismanaged events in Iraq. Yesterday morning, however, he offered a qualified mea culpa in aphone interview on the Don Imus syndicated radio show, which is also televised on MSNBC.

"This comment couldn't have been directed at them [soldiers in Iraq] because you can't get into the military by doing badly at school. This was directed at the people who didn't do their homework, didn't listen to history, didn't listen to their own advice, and they owe the American people an apology," he said.

As the day progressed with no ebbing of criticism, he issued the more thorough apology.

House Majority Leader John Boehner, R-Ohio, who had been among the Kerry critics, said in an interview on CNN that he thought the apology would bring the matter to a close.

But six days before the election, the GOP is sure to continue to mine the controversial remarks for as much value as it can.