Washington ? South Carolina Gov. Mark Sanford’s admission of an affair Wednesday dealt a potentially fatal blow to the political career of a rising Republican star, and it’s only the latest stumble of many in the early jockeying to lead the GOP back from oblivion in 2012.

A number of potential Republican presidential candidates recently have suffered missteps or other circumstances that threaten to shake up the race long before it formally begins.

They range from the most politically lethal — public confession of extramarital affairs — to less serious setbacks, such as a botched speech just as the world was watching, or being tapped to serve in the Obama administration.

Each of these incidents underscores the high stakes for a party searching eagerly for a new leader to fight back against the Democrats, who control Congress and the White House.

For Sanford, whose opposition to President Barack Obama’s federal spending propelled him into the national spotlight, the admission of an affair after being missing for five days likely ended what was a solid shot at the nomination.

“It’s very tough for him,” said Greg Mueller, a conservative strategist and a veteran of Republican presidential campaigns.

“The Republican Party will want someone without any baggage. We have an enormous task ahead. Anyone with baggage is going to be a problem. And we are less accepting of these kinds of situations than the Democrats. They’ll keep a lying, cheating guy in the White House like Bill Clinton. We won’t.”

Tarnished images

Among the once-plausible GOP candidates:

• Sen. John Ensign of Nevada admitted an affair and resigned as the chairman of the Republican Policy Committee, one of his party’s leadership posts in the Senate.

• Former House Speaker Newt Gingrich had to back off after calling Supreme Court nominee Sonia Sotomayor a racist, and also carries personal baggage from two divorces.

• Gov. Bobby Jindal of Louisiana was criticized for his performance on national TV when he was tapped to give his party’s response to Obama’s address to a joint session of Congress in February. One writer at the conservative American Spectator said that Jindal “seemed more like a high school student giving a valedictory speech than a potential future leader of the party.”

• Gov. Rick Perry of Texas suggested that his state might secede from the union over complaints about the size of the federal government.

• Gov. Sarah Palin of Alaska remains an exciting voice to conservatives, with enormous fundraising potential, but she continues to struggle with her image. In recent weeks, she’s upset party members with crossed messages about whether she’d appear at fundraising events and other party gatherings, and her family members’ soap-opera-like travails haven’t helped either.

• Gov. Jon Huntsman of Utah, a rising star mentioned as a possible Western challenger and taken seriously by Democrats, was taken out of the early competition by the White House when Obama named him ambassador to China.

In the running

Still, several potential candidates remain viable:

• Gov. Haley Barbour of Mississippi. A polished former chairman of the Republican National Committee, Barbour discounts talk of a candidacy by saying that voters likely wouldn’t choose someone who once was a lobbyist. However, insiders say he’s thinking seriously about it. And he’s hitting Iowa and New Hampshire, two must-stops on the road to the nomination. Wednesday, Barbour was tapped to lead the Republican Governors Association, replacing Sanford, who stepped down.

• Former Gov. Mike Huckabee of Arkansas. He won the Iowa Republican caucus in 2008, but never caught fire after that. He’s written a book since then and hosts a program on Fox News. He’s still popular with Christian conservatives, but still has no obvious fundraising base.

• Gov. Tim Pawlenty of Minnesota. He was on the short list to be John McCain’s running mate, losing out to Palin. He scored with conservatives at the end of this year’s state legislative session when he refused to raise taxes to close a budget gap. He recently said he won’t run for a third term next year, freeing him to run full time for the nomination.

• Former Massachusetts Gov. Mitt Romney. His 2008 campaign was hit by charges that he was a closet moderate who flipped on issues such as abortion to court the conservative primary vote. But worries about the economy have bolstered his credentials as a business executive.

“It is early,” said Dennis Goldford, a political scientist at Drake University in Iowa. “Nobody first-rate has emerged yet. But if you go back to ’05, nobody major in the Democratic Party had emerged yet. And they went on to win it all.”