Massachusetts Sen. John Kerry insisted on Sunday his "botched joke" about President Bush's Iraq policy would not undermine a possible White House campaign in 2008.

"Not in the least," Kerry, the Democratic presidential nominee in 2004, said when asked if the furor over his comment had caused him to reconsider a 2008 race. "The parlor game of who's up, who's down, today or tomorrow, if I listened to that stuff, I would never have won the nomination."

One of the GOP politicians mentioned in a crowded field for the White House, former House Speaker Newt Gingrich, said he would not make a decision until September — a relatively late date in the campaign cycle — to focus in the private sector on trade policies.

"We have lots of time for personal ambition," the Georgia Republican said. "And I think an awful lot of this early energy is wasted, and we ought to be focusing on, you know, how are you going to compete with China and India, how are you going to solve the problem in Iraq?"

Gingrich said Arizona Sen. John McCain and former New York mayor Rudy Giuliani, both of whom have set up presidential exploratory committees, were the likely front-runners. But Gingrich said voters are yearning for a clearer conservative voice.

"I think Mitt Romney has an opportunity to fill that," Gingrich said, referring to the outgoing Massachusetts governor.

McCain said Giuliani was an "American hero" for his leadership in New York following the Sept. 11 attacks. But McCain called himself the best presidential candidate based on a "record of being a conservative Republican, of knowledge on national security and defense issues."

McCain, who supports a ban on abortion except in cases of rape, incest and to save a mother's life, said he doubted a constitutional amendment could pass but that one would not be needed because "it's very likely or possible that the Supreme Court should — could — overturn Roe v. Wade."

The high court is deciding this term whether to uphold a 2003 federal law banning the procedure opponents call "partial-birth" abortion in a case conservatives hope could be used to reverse the landmark 1973 abortion-rights decision.

At least two conservatives, Justices Antonin Scalia and Clarence Thomas, have called on Roe to be overturned. Legal analysts have said if the court issues an anti-abortion ruling, justices would be more likely to impose restrictions rather than abolish the right.

"I'm a federalist," McCain said. "Just as I believe that the issue of gay marriage should be decided by the states, so do I believe that we would be better off by having Roe v. Wade return to the states. And I don't believe the Supreme Court should be legislating in the way that they did on Roe v. Wade."

McCain called the military's "don't ask, don't tell" policy toward gays "very effective." He said he opposed gay marriage, but as to civil unions, "people ought to be able to enter into contracts, exchange powers of attorney, other ways that people who have relationships can enter into."

Kerry said he would decide early next year whether to run for president.

Shortly before the Nov. 7 elections that brought Democrats back into power in the House and Senate, Kerry retreated from public view following his remark to a college audience that young people might get "stuck in Iraq" if they do not study hard and do their homework.

"This is over. This was a misstatement. All of us make them in life. You wish you could have it back, but you can't," the senator said Sunday.

Kerry said Sunday he had made the decision to keep a low profile after the White House attacked the joke as insulting to U.S. troops and several Democrats called the comment a needless distraction before the pivotal congressional elections.

"Since we had very close races, I made the decision to make certain that I didn't distract. The results speak for themselves," he said.

On running in 2008, Kerry said he had not yet made a decision whether to set up an exploratory committee.

"Right now, my focus will be what happened on election day," he said, citing a need to work toward solutions on Iraq, energy independence and health care. "The American people are waiting for us to lift up an enormous challenge."

Both Kerry and Gingrich appeared on "FOX News Sunday." McCain was on "This Week" on ABC.