WASHINGTON – Frustration over the prolonged Iraq conflict exploded onto the political scene Tuesday as Republicans pounced on John Kerry for a botched joke, while the Democrat slammed back at President Bush’s “broken policy.”

With tensions escalating and the stakes high just a week before the midterm elections, the president led a GOP chorus demanding the Massachusetts senator apologize for a remark about how the uneducated “get stuck in Iraq.”

But a furious Kerry refused to back down, saying he would never apologize for taking on the president – and that the criticism against him was orchestrated by “assorted right-wing nut jobs.”

Kerry is thought to be eyeing another White House run after losing to Bush in 2004. But fallout from his flubbed line could endanger his ambitions – and may even torpedo Democrats’ dreams of regaining control of Congress in next Tuesday’s election.

In a speech Monday at Pasadena City College in California, Kerry opened with some one-liners, then said: “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.”

Bush called the comment a major dis to U.S. troops.

“The senator’s suggestion that the men and women of our military are somehow uneducated is insulting and it is shameful,” the president said. “The senator from Massachusetts owes them an apology.”

An angry Kerry insisted the line “was a botched joke about the president and the president’s people, not about the troops.”

His office said he meant to say it was the administration and its allies who were not smart and got “us stuck in a war in Iraq.”

“I apologize to no one for my criticism of the president and of his broken policy,” Kerry fumed. “If anyone owes our troops in the fields an apology, it is the president.”

Kerry, a decorated Vietnam veteran, also lashed out at “despicable Republican attacks” from “those who never can be found to serve in war.”

“If anyone thinks a veteran would criticize the more than 140,000 heroes serving in Iraq and not the president who got us stuck there, they’re crazy,” he said in a statement.

GOP Sen. John McCain of Arizona – like Kerry, a Vietnam vet and potential 2008 presidential hopeful – also said the Democrat should apologize.

With the mood soured against them, in large part because of Iraq, Republicans could hardly believe their good luck in getting a distraction so close to next Tuesday’s election.

“It’s unbelievable that he’s pushing back so hard,” said Brian Nick, a spokesman for the National Republican Senatorial Campaign. “This is a base election, and this energizes the base.”

Pained Democrats didn’t rush to Kerry’s defense, but predicted the flap wouldn’t matter.

“The Republicans saw an opening and they took it,” said a top strategist. “We’re going to keep the focus on Iraq.”