Don’t look now, but it’s becoming very clear that Mitt Romney is starting to solidify his grip on the Republican nomination. The latest signs of this came over the weekend, in the form of two new endorsements from New Hampshire, Senator Kelly Ayotte and Representative Charles Bass. Bass constitutes the 43rd member of Congress to endorse Romney — Rick Perry is next with 14, and current polling co-leader Newt Gingrich has only 6, four of them from Georgia.

What’s interesting is that for most of the year, Romney had only a mild lead in endorsements. In fact, what was most notable about the GOP race all year was the lack of high-profile endorsements for any candidate. Over the last few weeks, however, that’s starting to change, a likely sign Romney is pulling away from the pack.

The political science literature tells us that high-profile endorsements are important indicators for at least two reasons. One is that these endorsements probably have a direct effect, as primary voters with little way of choosing from among similar-sounding candidates may turn to opinion leaders to sort things out. The other, and perhaps more important, factor is that high-profile endorsements are the most visible ways of seeing the co-ordination of party actors as they compete over the nomination and eventually settle on a candidate. That is, if politicians and party-aligned interest group leaders are willing to place their name with a candidate, it probably means that others within the party — ctivists, donors, campaign and governing professionals, and other, lesser-known politicians — are moving towards that candidate as well.

What’s really interesting here is that apart from some solid success by Rick Perry over the summer, none of the other bubble candidates (Gingrich, Herman Cain, Michele Bachmann) have had any luck at all attracting high-profile endorsements. That’s one of the key reasons not to take any of those candidates very seriously; it means that top Republicans don’t take them seriously. What we’re seeing now is that Rick Perry’s awful fall appears to be taking a toll: Party actors willing to wait for him to get his act together are losing patience; they’re also giving up on their hope for some white knight to come swooping in to save them from the Mittster.

Is it over yet? Not quite. But it’s getting there. Once a party-led bandwagon starts really rolling, it can be awful hard to stop. It’s looking more and more as if Romney has an excellent chance of wrapping this thing up by New Year’s Day, leaving the voter portions of the contest as a mere exercise in how, not whether, he will win it.