An eventful day jolted the Republican presidential campaign Thursday, as the candidates prepared for a key debate.

Frontrunner Mitt Romney, the former governor of Massachusetts, faced new challenges, as polls show rival Newt Gingrich cutting into Romney's lead two days before the South Carolina primary election. Part of the Gingrich gain, some political analysts say, is the result of his strong performance in a debate earlier this week.

Gingrich is the former speaker of the U.S. House of Representatives. He stood to gain further after Texas Governor Rick Perry ended his campaign for the Republican nomination. Perry threw his support to Gingrich.

But Gingrich also faces new challenges – from an interview that his second wife, Marianne, gave to ABC News. In an an excerpt of the interview to be broadcast later Thursday, Marianne Gingrich says her former husband asked that she “accept the fact that he has somebody else in his life” — the former Callista Bisek, who married Gingrich in 2000.

Marianne Gingrich, former wife of presidential candidate Newt Gingrich:))

Although he has been married three times, and acknowledges that he had affairs during his first two marriages, Gingrich has strong support among social conservatives.

Later Thursday, Romney and Gingrich join fellow candidates Ron Paul, a Texas congressman, and Rick Santorum, a former Pennsylvania senator, in a televised debate.

Santorum's candidacy got a bit of boost early Thursday, when Republican officials in the state of Iowa said he captured the most votes in the state's January 3 caucuses, not Romney. Initially, Iowa Republican officials said Romney unofficially won the caucuses by eight votes, and Santorum, a social conservative, came in second.

But after certifying the votes, Iowa party officials on Thursday said Santorum finished with 34 more votes than Romney. However, they did not declare Santorum the official winner because vote tallies from eight caucus gatherings are missing and will never be recovered.

Despite Gingrich's surge in the polls in South Carolina, many political analysts view Romney as the eventual Republican nominee. But some Republicans view the one-time venture capitalist as not conservative enough.

The country's weak economy remains the top issue in the campaign. And in recent weeks, Romney's rivals have hammered at him because his venture capital firm often bought companies and then dismantled them or laid off workers to make them more profitable. They also have opposed the health care reforms he instituted as governor of Massachusetts.

The South Carolina primary on Saturday is seen as a possible turning point for the campaign. A decisive win for Romney could put him in a commanding position to win the Republican nomination and challenge President Barack Obama for the presidency.

Mr. Obama, a Democrat, is running unopposed.