Calls for Gov. Mark Sanford's resignation began to mount Thursday, one day after he shocked South Carolina by revealing that his marital infidelity was the reason behind his recent absence.

Most lawmakers and state leaders, even Sanford's supporters, refrained from any show of support and wondered what further details might emerge that would affect his ability to remain in power.

"A lot of people are waiting to hear more information or more facts so when they do make a judgment, it's an informed judgment," S.C. Speaker of the House Bobby Harrell said. "Yesterday's revelations were pretty shocking to a lot of us. Folks are sorting out that information and learning new information before they start expressing opinions."

Both state Rep. Todd Rutherford, D-Columbia, and State Republican National Committeeman Glenn McCall asked for Sanford's resignation.

Others were unwilling to go that far yet, but the chorus of criticism increased. Former U.S. Sen. Fred Thompson, a Republican presidential candidate in 2008, weighed in on Sanford, a potential 2012 GOP candidate, on his Web site.

"I don't have any sympathy in a situation where you've got a wife and four fairly young kids," Thompson said. "Don't play it out in public."

Sanford donor Al Hill of Dallas-based AG Hill Partners, an investment firm, was having a letter drafted Thursday requesting that money given to the governor's campaign be immediately returned, The Associated Press reported. The company gave $3,500 for Sanford's 2006 race.

"And now we are asking that it be sent back," said Joy Waller, an assistant to Hill. "Do you even have to ask why?"

One of Sanford's harshest critics, State Democratic Party Chairwoman Carol Fowler, said her thoughts were with Sanford's family.

"Mark Sanford should be given time to focus on his family right now," she said. "There will be other opportunities in the weeks ahead to discuss his effectiveness as our state's governor."

Another critic, Senate Democratic leader John C. Land, D-Manning, also stopped short of calling for his resignation. But Land noted that Sanford's comment that he will work to rebuild trust would distract him from addressing pressing problems, such as the state's high unemployment rate. Even in this crisis, Land said, "Sanford's still thinking about what's best for him, not what's best for the state."

It was too early Thursday to predict if Sanford will hold onto his job, according to Barbara Kellerman, the James McGregor Burns lecturer in public leadership at Harvard's John F. Kennedy School of Government.

She said that depends on what happens next, including how contrite he appears, whether his family stands behind him, and whether public money was involved in carrying on the affair.

Sanford made a 2008 business trip to Argentina at taxpayers' expense and saw his mistress at that time. As soon as that story broke Thursday, he defended the trip as appropriate but also announced he would reimburse the state for the full cost of the Argentina leg.

Fowler said such reimbursement was appropriate but raises more questions than it answers. "How many other times has the state paid for him to spend time with this woman? I think rather than letting it all trickle out, he would be well served to lay it all on the table."

Complicating any decision to resign would be the advantage that would give Lt. Gov. Andre Bauer, who would see his 2010 gubernatorial election hopes soar if he could run as the incumbent in the crowded GOP primary field. Most believe Sanford favors other candidates in the race, particularly state Rep. Nikki Haley, R-Lexington.

State Sen. Larry Grooms, R-Bonneau, is considering running for governor, and he said Thursday he was disappointed in the governor.

"The conservative reform movement has been set back greatly by his actions," he said. "On a personal level that really hurts because that's what I've been pushing for.

"Nothing can excuse the governor's behavior, and out of respect for him and his family, I don't think it's a good idea to comment right now on whether he should or should not resign. I believe the governor loves the state and, given enough time, I think he will make the right decision."

S.C. Attorney Gen. Henry McMaster, also a gubernatorial hopeful, released a one-sentence statement saying only, "Until all the facts are known, any speculation regarding potential action by this office is premature."