Despite Newt’s tenuous lead in the polls, the real story of the GOP primary is that bit by bit the party is deciding, and so far they’re deciding for the Mittster.

Today’s Romney endorsement — South Carolina Governor Nikki Haley — is a significant one. She’s on the Post’s list of 50 “most coveted endorsers,” and she’s one of the five who I said here last week were the most important ones to watch.

There is a bit of a paradox with endorsements. By themselves, few endorsements really do much. They don’t bring (as they did before 1972) blocks of convention delegates. They may bring tangible campaign resources (money, publicity, organization), but most do not, at least not in any significant way. Very few voters are consciously waiting for marching orders from their favorite Republican on how to vote. And any particular endorsement can turn on purely idiosyncratic and personal reasons, and therefore have little predictive value for what other party actors are thinking.

But put together in larger patterns, endorsements are incredibly important, and even decisive. That’s because, put together, endorsements provide a clue into what party actors are collectively thinking. In particular, for Mitt Romney, they’re a clue about whether conservatives are going to find him acceptable. And back-to-back endorsements from Tea Party favorites Christine O’Donnell and Nikki Haley? A very nice week for Romney.

It certainly can’t hurt having the governor of a key primary state in one’s corner, even if she’s had a rough year and isn’t very popular overall in the state. Collectively, party actors control plenty of money, organization, and publicity, and it’s highly unlikely that anyone can stand against them if they agree on a candidate. We’re not quite there — Haley gives Romney just a 6-3 lead over Rick Perry among the Post 50, with 41 remaining undeclared, so there plenty of time left for another candidate to surge into the lead. But bit by bit the party is deciding — for the Mittster.