I had a phone conversation today with a prominent scholar at a conservative think tank who has served in several Republican administrations. He was glum. He asked plaintively, “Are we really stuck with Romney?” He then asked me “So who’s the least midget-like of the other midgets?”

He was a telling comment, a recognition that the not-Romney options are becoming untenable for a great number of conservatives. They find the alternatives lack in presidential temperament or are devoid of experience or simply in over their heads. And yet, the conservative I spoke to is still not sold on Mitt Romney. Like many on the right, his sense is that Romney may be the only credible candidate in the race now, but he remains mystified that there is not a more robust, credible not-Romney in the race.

There are a couple of options for such Republicans. One is to go back to the well and try to lure back in one of those who previously decided not to run. Some still pine for Rep. Paul Ryan (R-Wis.). At some point, however, that option becomes (if it hasn’t already) unfeasible. I had to break it to my conservative think tanker that, barring some bolt of lighting, this is the field from which Republicans will choose their presidential nominee.

No votes have been cast and no one is really “ahead” in the presidential primary. (They may lead in a poll, but that’s an entirely different matter.) So there is no reason for not-Romney conservatives to throw in the towel.

For one thing — and I think this is key — Romney should have to earn their votes. He should step up to the plate with a complete tax reform plan. He should show more leg on Medicare. He needs to convince conservatives he has conservative convictions? Well, the best way to do that is in outlying his policy preferences.

The usual pattern is run right in the primary, to the center in the general election. But in this case Romney’s been running his general election campaign. At some point he’s going to have to take a detour and excite the base, thereby unifying the party.

If the field narrows to one or two competitors he’ll have to do that during the primary process to win the nomination. But whether before or after tallying up the votes for the nomination Romney, if he is to be the nominee and to have the full conservative army at his side, will have to make sure the right is committed to his candidacy.

Some say that the mere opportunity to rid the White House of Obama will be sufficient. That may be. But, I believe, there is one item that could take on unique importance in this election: the selection of his running mate .

For conservatives that pick is an investment in the future, setting the scene (whether Romney wins or not) for a movement conservative to be in the pole position for the next open presidential nomination. It’s also some insurance that a true conservative voice will be heard in th White House. Given the last two vice-presidents’ influence, there is the potential that a strong VP would have exceptional influence in discrete policy areas.

Romney correctly has not discussed what sort of running mate he’d pick. He’s got enough problems convincing voters he doesn’t presume himself to be the winner before the race begins. But he and the conservative base should tuck this away should it become necessary: The pick may be critical to engage conservatives’ passion (much as it was in 2008). Those who are not disposed to Romney will say this wouldn’t make up for a movement conservative at the top of the ticket. They are right. But by the same token should he need to reconcile with base conservatives, Romney would do well to consider whether a superstar conservative running mate would be an appropriate peace offering.