Mitt Romney hopes that the endorsement of the ABM Caucus will propel him to the White House.

ABM, in this case, does not stand for “Anti-Ballistic Missiles,” but rather “Anyone But McCain.”

Recently, Romney has had a boomlet of endorsements from House Republicans, including former Speaker Dennis Hastert (Ill.), Jim McCrery (La.), Buck McKeon (Calif.), Tom Feeney (Fla.) and Marsha Blackburn (Tenn.). Former Rep. and now-Sen. Jim DeMint (S.C.) is also on board, and there have been rumors that Minority Leader John Boehner (Ohio) will jump on the Romney bandwagon. For this early in the campaign, it is a pretty good list, especially for a former governor with no Washington experience.

What these endorsements have in common is that they come from a substantial group of House Republicans who have long disliked John McCain. For many House Republicans, McCain was the antithesis of what they were fighting for. The House would move conservative legislation, only to see the Senate water it down, and McCain was seen as the “waterer-down in chief.” His House critics disliked his working with Democrats. They remembered his championing of campaign finance against the majority of the House majority’s wishes.

These House Republicans are looking for an alternative, and so far, Romney has been the candidate to capitalize on these lingering resentments.

Romney is looking for a niche in this strange Republican field, which is full of mavericks but has a hole in the traditional mainstream conservative Republican slot. There is room for another candidate to the right of McCain and to the left of Brownback. George Allen (R-Va.) would have filled that space had he not self-destructed in his Senate race.

I have argued in this column that recent events surrounding the war have not benefited McCain, but he is still the frontrunner in the Republican field. It will likely come down to McCain and someone else, and Romney is angling to be that other candidate.

Romney, of course, has his own definitional problems. Is he a liberal Massachusetts Republican or a conservative Utah Mormon Republican? To his benefit and detriment, he has been a little of both. In another Republican field, he might have run as McCain did in 2000 — as the maverick appealing to moderate Republicans and independents. But that turf is too crowded with McCain, Giuliani, Pataki, and perhaps Sen. Chuck Hagel (Neb.).

To get to the right of McCain, he has trumpeted his stand in Massachusetts against gay marriage and reversed his position on abortion.

The issue that many believe Romney will use as a wedge between himself and McCain is immigration. McCain is firmly committed to a comprehensive plan along the lines proposed by President Bush. Romney has flirted with striking a more anti-immigration stance, which would endear him to a good portion of the Republican base and to many House Republicans. But as Sam Youngman reported yesterday in The Hill, Romney remained silent on the issue at a recent conservative summit.

McCain has made many strides mending fences with religious conservatives and Bush supporters; he has hired many talented Bush campaign veterans. But the divide between McCain and many House Republicans is too great to bridge.

House endorsements by themselves are worth almost nothing. But Mitt Romney is hoping that they send a signal to the wider world of Republican primary voters, party activists, and conservative donors that he is the real Republican in the race.

Fortier is a research fellow at the American Enterprise Institute.