The 2012 GOP presidential field is looking unusually and unexpectedly small after Mississippi Gov. Haley Barbour’s (R) decision Monday not to run for president.

Barbour, fresh off a trip to New Hampshire that had injected considerable buzz into his potential candidacy, promptly announced that he cannot invest himself into a presidential campaign, saying he’s not sure if he has the requisite desire.

“Supporters expect and deserve no less than absolute fire in the belly from their candidate,” Barbour said. “I cannot offer that with certainty, and total certainty is required.”

Barbour becomes the latest major potential presidential candidate to say no, joining Sen. John Thune (R-S.D.) on the sidelines and delivering what could be a game-changing decision.

So where does this leave us? A few thoughts:

Clearing the way for Daniels?

Barbour and Indiana Gov. Mitch Daniels are good friends and have said publicly that they didn’t want to run against each other. And for the longest time, it was assumed by most political observers that Barbour was the more likely presidential candidate.

With Barbour gone, a significant impediment to Daniels running is now out of the way, and those who know the governor say his decision just become a little (emphasis on little) easier.

All of that said, there is still considerable doubt that Daniels will run, and it’s no cinch.

Daniels is expected to make his decision in the near future.

And what about Huckabee?

If you’re keeping score at home, Sarah Palin’s poll numbers have nose-dived and Barbour is not running for president. If you’re Mike Huckabee, you have got to be pinching yourself.

More than anything, Barbour’s exit means the only other true southerner in the field is out. Meanwhile Huckabee keeps polling like the most liked candidate in the GOP field.

Things are slowly coming together for Huckabee, and as we’ve said before, at some point it’s going to be very hard for him to say no.

At the same time, Barbour’s quote about not having the “fire in the belly” is also telling when it comes to Huckabee. Put plainly: Huckabee needs it too. And without it, he could be offered the nomination on a silver platter and still turn it down.

Practical effects

As another potential frontrunner bows out, the vacuum in the primary field only grows.

The question is whether that means other candidates might start to look at the race or it just means the field of candidates will be that much smaller.

One thing it does mean is that Barbour’s many donors and loyalists are now fair game for everybody else in the field, and for such a well-connected Republican with such good people around him, there’s a lot to be mined.

Through his entire process of considering a presidential run, Barbour has been turning himself into a potent potential endorser. We’ll see if he uses it.

Early stuff matters

The fact is that the presidential race begins even before the presidential race begins, and it wasn’t always kind to Barbour.

The governor got tripped up when he suggested the Civil Rights era wasn’t that bad in his home town, and then a staff member got caught sending off-color jokes via e-mail, among other issues.

Even before the launch of an exploratory committee, a potential candidate is being vetted by some important people in the presidential nominating process: experts, the media, Republican operatives and donors.

Barbour already had obstacles as a southern governor with a thick accent and a lobbying past that can be tied to the tobacco industry, and he wasn’t making things easier on himself.

Which could be part of the reason why he didn’t have the fire in the belly to jump into the race, even after sending plenty of signals that he did.