Newt Gingrich’s former Republican colleagues in the House are more than a little nervous about the prospects of sharing a ticket with him in November.

They think he’d run weakly in the suburbs. And among women. And independents. And especially in the Northeast.

To some of them, he’s a disaster in the making, a potentially combustible nominee who could, in a worst case scenario, cost the GOP its newly minted majority.

The concern is serious enough, one freshman Republican told POLITICO, that on the bus ride back from the House GOP retreat in Baltimore last week, Gingrich’s electability was the prime subject of discussion among nearly a dozen members — many of them first-termers.

Several conservative female lawmakers “recoiled” at the thought of Gingrich at the top of the ticket, according to the Republican.

A key concern expressed in the conversation was whether Gingrich would appeal to suburbanites — a demographic critical to the reelection hopes of many GOP House members.

“When I saw the reaction from conservative women, it scared me,” said the freshman who, like several other members interviewed for this story, spoke only on the condition of anonymity. “He needs to let us know how he’s going to appeal to suburban independents if he’s the nominee.”

Northeastern Republicans, a regional class of members who faced near-extinction after suffering big losses in 2006 and 2008, are particularly unnerved by Gingrich’s rise.

“I absolutely think it’s going to matter who’s at the top of the ticket,” said a House Republican from the region.“I think the prevailing wisdom is that in the Mid-Atlantic and Northeastern population centers, Romney would be a better candidate to help the ticket. Those areas are where you have a large population of swing state voters.”

While close to a dozen members of Congress have endorsed Gingrich, that figure is dramatically less than Mitt Romney, who’s been endorsed by roughly a quarter of the Republican conference. The bulk of them are from just two states, Georgia and Texas.

While many Capitol Hill Republicans view Romney as an imperfect candidate, the thinking is that’s he’s more broadly palatable to voters and there’s far less of a chance that he would damage the party’s prospects down-ballot.

In soliciting support on Capitol Hill, Romney has sought to highlight his potential reliability as a Republican nominee. At a closed-door meeting with GOP lawmakers last year, Romney offered this promise to the more than 60 members of Congress who came to hear him.

“I won’t embarrass you,” he said.