As Newt Gingrich surges again, Congressional Republicans remain fearful that the former Speaker would lose to President Barack Obama and sink the whole GOP ticket in the process if he were nominated.

In interviews Monday, neutral Republican operatives and GOP Members backing ex-Massachusetts Gov. Mitt Romney said nothing they have observed over the course of the 2012 presidential campaign has assuaged their fears about a Gingrich candidacy. The worries are not policy-based; they’re personal and attributed to Gingrich’s conduct both as Speaker and as a conservative activist and lobbyist since leaving Congress.

“I’ve said all along that I think Romney is our best general election candidate, I think the person best positioned to win the election and defeat the president, and I still hold that view,” Sen. John Thune (R-S.D.) said. “I think it’s going to be important for all of our candidates and all our campaigns [this] year to have a top of the ticket that we can coordinate with and work closely with to try and elect more Republicans to the House and the Senate. It’s been my view all along that the person that’s best positioned for that is Romney.”

Thune, the Republican Conference chairman and No. 3 in Senate GOP leadership, endorsed Romney in November and campaigned for him in Iowa.

Most Congressional Republicans who have endorsed in the 2012 race are backing Romney, calling him the most conservative candidate running who is also electable in a general election matchup with Obama. Republicans also believe a Romney candidacy would give their party its best chance to hold the House majority and flip the four seats needed to capture the Senate. Unaligned Republican strategists say Romney gives the party its chance to win seats in competitive districts and states.

Given the volatility of the GOP primary campaign, Republican Members were hesitant to comment publicly.

But privately, they lack confidence in Gingrich’s ability to organize and lead a national campaign that can compete with the Obama machine. They also worry that Gingrich is an entrenched Washington figure unable to reboot a public image that his GOP critics say is toxic with swing voters, independents and women. Recent polling has shown Gingrich’s personal favorability to be in the high 20s, with his unfavorable rating north of 50 percent.

“You want the campaign to be about the incumbent and his failed record on the economy. With Newt Gingrich, it’s hard for it to be about the other guy,” said one Republican Member who served in the House when Gingrich was Speaker.

Gingrich surged back into contention in the presidential primary with a strong victory in South Carolina on Saturday. He has closed the gap with Romney in national polls and now leads Romney in surveys of Florida GOP voters, who go to the polls Jan. 31, leading some to describe him as the primary’s new frontrunner.

Gingrich, who has the backing of nearly a dozen Republican Members compared with Romney’s 72, has charged the GOP establishment with opposing his nomination because it fears the change he would implement in Washington if he was elected president.

Sen. Roy Blunt (R-Mo.), who is running Romney’s whip operation on Capitol Hill, dismissed that argument, saying support for the former Massachusetts governor is based on who is best equipped to win the election and serve as president.

“Lots of things will be said in the primary, and most of them won’t really matter very much as soon as the nominee is selected,” Blunt said. “I’m for Romney. I think he is the most likely to get elected, and I think he’d be a good president.”

One Republican political consultant based in California said he doubted a Gingrich loss against Obama would sink GOP candidates lower on the ticket. But he predicted that a Gingrich candidacy would create challenges for the party.

The consultant said Republican campaigns would have to turn out GOP voters despite polling that might show Gingrich trailing Obama, while focusing on encouraging voters who might want to vote Republican but can’t stomach Gingrich to split their ticket.

“Other than a convention bounce, it’s hard to imagine Gingrich ever sustaining a lead in the polls, and thus the narrative will become defeatist,” the operative said. “So we’ll have to convince more swing voters to vote GOP for Congress after they vote against Gingrich.”