WASHINGTON - Republican lawmakers, who have spent months seeking to tie President Obama to last year's deadly attack on the U.S. diplomatic mission in Benghazi, are increasingly focusing their probe on a new target: former Secretary of State Hillary Rodham Clinton.

The GOP-led investigation of the Sept. 11 assaults that killed U.S. Ambassador J. Christopher Stevens and three others now centers heavily on the State Department and whether officials there deliberately misled the public about the nature of the assault.

Three State Department officials are scheduled to testify before a House committee on Wednesday about the Benghazi attack and its aftermath. GOP investigators have also become particularly interested in a fourth State Department official, Victoria Nuland, a spokeswoman under Clinton who reportedly played a role in the revision of talking points at the heart of the controversy.

"I think the dam is about to break on Benghazi," Sen. Lindsey Graham (R., S.C.) wrote on his Facebook page Tuesday. ". . . We're going to find people asleep at the switch when it comes to the State Department, including Hillary Clinton."

On Monday, a Fox News anchor asked Rep. Darrell Issa (R., Calif.) how damaging the issue is for Clinton. "I think it's damaging because it happened under her watch," replied Issa, chairman of the House Oversight and Government Reform Committee, which is holding Wednesday's hearing.

To Democrats, the efforts amount to a baseless crusade to tarnish the credentials of Clinton, one of the country's most popular political figures and the overwhelming favorite for the 2016 Democratic presidential nomination.

"This is the same political exercise as before, with just a different target in mind," said Rep. Adam Schiff (D., Calif.), a senior member of the Select Committee on Intelligence. "They're no longer going after the White House, perhaps because the president's not running for reelection, and they're going after the former secretary of state, perhaps because she will be."

Frederick Hill, a spokesman for Issa's committee, denied that partisan politics were involved. "The motivation of the committee is to bring forward information that has been pushed away from the public," he said.