GREENVILLE, S.C. (AP) — Newt Gingrich didn't know when he would take office if he wins the presidency. Rick Perry got the voting age and the date of Election Day wrong. Herman Cain didn't realize the president does not sign amendments to the Constitution.

In ways large and small, Republican presidential hopefuls are proving on multiple occasions to be "factually challenged," as Gingrich rather haughtily described a rival, despite getting some things wrong himself.

Campaigns are long and tough, candidates are often tired and flubs happen. But they are adding up and at some point could give Republican voters pause as they look for the candidate best able to take on the highly polished — though hardly factually infallible — President Barack Obama.

In submitting to what is, in effect, America's toughest job interview, there may be only so much leeway in getting matters of current affairs and history plain wrong.

Frequent flubber Michele Bachmann's suggestion many months ago that the Revolutionary battles of Lexington and Concord took place in New Hampshire was an opening shot, of sorts, in a volley of misfires by the candidates. Those battles were fought in Massachusetts in 1775.

On Wednesday, she offered another: She would support the United States shutting down its embassy in Tehran — but there is no U.S. Embassy in Iran's capital.

Never mind the facts, her top spokeswoman said. "Congresswoman Bachmann is a member of the House Select Committee on Intelligence and is fully aware that we do not have an embassy in Iran and have not had one since 1980," Alice Stewart said in a statement.

It's the latest but hardly the worst.

Cain promoted Chile's retirement system as one that gives workers the option of having private accounts, when in fact they have no choice. Mitt Romney accused Obama of "peacetime spending binges" as if there were no wars going on. Bachmann accused Obama of canceling a Canadian pipeline project that has only been delayed.

On Wednesday, Gingrich told voters packed into Tommy's Country Ham House in Greenville, S.C., that he would sign legislation repealing health care and Wall Street overhauls when he takes office on Jan. 21, 2013.

"My intent will be to ask the new Congress to stay in session when they are sworn in on Jan. 3 and to pass — and hold at the desk until I'm sworn in on the 21st — to pass the repeal of Obamacare and the repeal of Dodd-Frank and the repeal of Sarbanes-Oxley so that I can sign them on the 21st," Gingrich told the packed restaurant.

One problem: the Constitution that Gingrich constantly cites during his presidential campaign says the transition of power after an election takes place on Jan. 20.

Gingrich spokesman R.C. Hammond said Gingrich would assume powers at noon on Jan. 20, 2013, following the 20th Amendment of the Constitution. Because that day is a Sunday, the Inauguration's festivities would be scheduled on Jan. 21 of that year. Ronald Reagan followed a similar schedule for his second inaugural on Monday, Jan. 21, 1985.

Even so, Gingrich was wrong to say "I'm sworn in on the 21st."

A day earlier, Texas Gov. Rick Perry suggested the voting age is 21 and got the date wrong for Election Day.

"Those of you that will be 21 by November the 12th, I ask for your support and your vote," he told students at Saint Anselm College in New Hampshire.

The voting age is 18. And New Hampshire is scheduled to be the first state in the nation to host a Republican presidential primary on Jan. 10; the general election is scheduled for Nov. 6, 2012.

Cain said he would back an amendment to the Constitution to ban abortion.

"If we can get the necessary support and it comes to my desk, I'll sign it," he told the Christian Broadcasting Network.

Except presidents don't sign amendments. Congress passes them and the states ratify them. The president could champion them, but the Constitution doesn't give him or her any formal role.

Since the campaign's start, each candidate has had a turn explaining errors as either the side effects of an exhausting schedule or simple foot-in-mouth syndrome. Under the intense media scrutiny, each misstep or error draws questions whether each candidate is up for the job.

Romney, too, stepped in it. The former Massachusetts governor said Obama engaged in "one of the biggest peacetime spending binges in American history." He overlooked the United States' role in conflicts in Iraq, Afghanistan and Libya.

Yet not all errors are created equal, said Eric Dezenhall, an aide in the Reagan administration and now an image consultant who has worked with everyone from Hollywood stars to business moguls.

"The key factor in whether a gaffe catches on is whether or not it validates a pre-existing prejudice," he said.

"When Perry says that the voting age is 21, it validates the pre-existing suspicion that he's not in command of the basics," he said. "When Newt or Obama say something that is either misguided or incorrect, it doesn't resonate because everybody knows they are smart guys, so they get a break."

And it's not as if Obama hasn't had his doozies. For instance, Obama said during the 2008 campaign that he had visited 57 states. The United States only has 50.

"The flubs that stick are those that fit with a storyline about the candidate," said Doug Hattaway, a Democratic consultant who helped Hillary Rodham Clinton's 2008 presidential bid. "Gingrich isn't a flubber. He's known for being full of himself and making wacky statements, not flubbing the facts. So the misstatements are less likely to stick to him."

And voters might not care about factual details, Hattaway said.

"Best case of that is George W. Bush, who couldn't pass a civics quiz to save his life. Emotional intelligence is more important in politics than factual knowledge," Hattaway said.

Gingrich might be playing that to his own political advantage.

Before he seemed to reschedule the constitutional transition of power, he criticized Bachmann for stretching the facts about his record on abortion.

"Some people are just factually challenged and it's unfortunate," Gingrich told reporters. "In the eyes of a teacher, occasionally I'd have a student who couldn't figure out where things were, or what things were, or what the right date was. When that happens, you feel sorry that they're so factually challenged."