[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/POLITICS/08/11/south.carolina.mark.sanford/art.mark.sanford.gi.jpg caption="Mark Sanford called the letter 'unpersuasive and unsurprising.'"](CNN) - An overwhelming majority of Republicans in the South Carolina House of Representatives called on Gov. Mark Sanford to resign Wednesday, saying in a letter hand-delivered to his office that the governor's actions "have been destructive to our state's image on a worldwide stage."
Sixty of 72 Republicans endorsed the letter that was signed by House Majority Leader Kenny Bingham on behalf of House GOP leadership.
The letter has been in the works ever since House Republicans met in Myrtle Beach last month during their annual retreat. At that meeting, not a single member of the GOP caucus spoke in support of Sanford and at least one legislator provided an outline of possible impeachment charges against the governor.
"The general sense of the Caucus is that the people of South Carolina have suffered enough as a result of your recent actions and the current allegations against you," the members wrote to the governor, referring to his disappearance from the state in June and subsequent investigations into his travel expenses.
The 60 members calling for the governor's resignation include a coalition of Sanford critics and allies, along with several legislators who would play key roles in the impeachment process if the House decides to try to remove the governor when the legislative session begins in January.
The letter was delivered one day after House Speaker Bobby Harrell broke his months-long silence and publicly called on the governor to step aside, making him the second-highest ranking elected official in the South Carolina to do so.
Despite the growing resignation drumbeat, it's unlikely that the letter from House members will do much to change Sanford's mind.
"The reality is King Herod's heart is hardened and Mark Sanford is not going to change his mind," one well-connected South Carolina GOP strategist said of Sanford's thinking.
The governor's office called Wednesday's letter "both unpersuasive and unsurprising" and pointed out that many of his longtime critics signed onto the letter, even though several allies - including Rep. Nathan Ballentine - added their names to the note.
"What this letter does provide is further evidence of a disconnect between the people of this state who want to move forward and many politicians in Columbia who see the current situation as a way to achieve political payback," Sanford's spokesman Ben Fox said in a statement.
Among the GOP House members not signing onto the letter: state Rep. Nikki Haley, an ideological ally of Sanford's who is running for governor in 2010.
Haley said in a statement that she decided not to support the letter because the governor has already made clear he will not step aside and any efforts to encourage him to do so amount to little more than political posturing.