This week's Supreme Court ruling on the Second Amendment right to bear arms and a vote on terrorist surveillance became the latest source of ammunition for John McCain supporters charging Barack Obama with flip-flopping, but Obama's backers don't have to search too far to find examples of their own.

Rob Portman, a Republican former Ohio congressman and Bush administration official, said Obama's reversals on the right to bear arms is only the latest in a string. Pennsylvania Gov. Ed Rendell, a Democrat and Obama supporter, pointed in response to McCain's recent turn-about on oil drilling, and others in recent years on the Bush tax cuts and immigration. The two -- who are said to be under heavy consideration for vice presidential candidates -- appeared on "FOX News Sunday."

The high court ruling overturned a Washington, D.C., ban on handguns inside residents' homes. The court also ruled that the right to bear arms is an individual right, not just the right of a "well regulated militia" that is cited explicitly in the Second Amendment.

Obama drew fire for saying this week he agrees with the opinion after last year he telling the Chicago Tribune that he believed the D.C. gun ban was constitutional. McCain called it "one in a long ... series of reversals."

Following up Sunday on the criticism, Portman said, "What Senator McCain was talking about is that late last year and again this year, Senator Obama did support he gun ban in D.C., and now he seems to have changed his position on that. And as Senator McCain indicated, he's (Obama) changed his opinion on a few other things, including public financing. Senator McCain's got a few decades of experience in being pro-gun. ... So I think there's a big distinction here between the two candidates."

Portman's attack on Obama for his decision last week to opt out of the public campaign financing system followed a pledge from Obama to talk with McCain about staying in the public finance system. Rendell said Obama never explicitly said he would stay in the public financing system. Obama stands to reap in significantly more money than the $84 million available to him through the public system by opting out.

Rendell sought to clarify Obama's positions on gun control, and pointed to McCain's own reversals.

"Senator Obama's position is very clear. The Second Amendment is an individual right. There's no question about that. Does it have limitations? Sure, it does. As Justice Scalia said in his opinion, this opinion doesn't mean that governments can't restrict the flow and distribution of guns. ... He's in favor of common-sense rules that will regulate the flow and distribution of guns, but he supports individual Americans' right to have both long guns and handguns," Rendell said.

As for McCain, Rendell painted him as someone whose record is full of position-switching.

"John McCain has switched positions on all of the the things that made independents and moderates and even some Democrats like myself think that he was a new type of Republican. These are core issues," Rendell said.

Rendell accused McCain of flip-flopping on immigration for pushing for border enforcement over comprehensive immigration reform; Portman countered saying the only reason was because comprehensive immigration reform legislation failed.

Rendell also defended Obama's apparent change of heart on the bill to update the Foreign Intelligence Surveillance Act. The bill, which stalled this week in the Senate, includes a controversial provision to grant immunity to telecommunications companies that secretly aided the Bush administration in wiretapping terror suspects in the days after the Sept. 11, 2001, attacks. Obama said he would support he provision, but earlier said he would not.

"When you're in the Senate, you have to weigh the entire bill," Rendell said. "The bill on FISA restored court supervision of wiretaps. That's a huge victory for individual rights in America. Senator Obama believed that was more important, that he had to go along and vote for it," even though it had the immunity provision. reviled by many Democrats. "Has pledged later on in the Senate to try to strip the immunity provision."

The candidates' evolving positions was the topic on other Sunday talk shows, too.

Rep. Rahm Emanuel, D-Ill. and high-ranking Democrat in the House who has endorsed Obama, leveled a barrage on McCain appearing on ABC's "This Week": "John McCain flip-flopped on taxes. ... Second, he referred to the evangelical community as agents of intolerance, and now he's embraced them. Third, he came out for oil drilling, once opposing it, after having received $800,000 from the oil and gas industry.

"If flip-flop was an Olympic sport, John McCain would be the first to win a gold medal."

Minnesota Gov. Tim Pawlenty, a Republican McCain supporter also said to be under vice presidential consideration, attacked Obama on trade, Iraq, and Israel.

Pawlenty, appearing with Emanuel, said Obama "says he's going to pull out of NAFTA unilaterally and then he has certain emissaries go up and whisper to the Canadian officials, 'well, we're just kind of kidding and maybe we'll do it gently.' Then he goes and says we're going to pull out of Iraq immediately. Then he has a meeting with the Iraqi foreign minister, where the minister says, well, maybe he's changing his position on Iraq and softening it.

"Then we have the issue where he goes to AIPAC and says we're going to have Jerusalem being the undivided capital, then he modifies that. And then he goes on and on and on down the list. The same with the Cuba embargo and several other key issues."

Pawlenty also took a swipe at Obama and Hillary Clinton's choice of locations to hold their fence-mending event Friday.

"They shouldn't have had the meeting in Unity, New Hampshire. They should have had it in Political Expediency, New Hampshire, if there is such a community. They had it in the wrong town," Pawlenty said.