Romney has officially thrown in the towel according to Associated Press. Huckabee vowed to stay in it. His role as the spoiler is over, so it's hard to understand what he has to gain by staying in. Clearly, remaining delegates will shift en masse to McCain leaving Huckabee even farther behind.
Romney cited as a reason for his decision the need for McCain to be able to launch his bid for the general election as soon as possible.
McCain has a difficult, but necessary, task in reaching out to Romney and Huckabee supporters. Social conservatives who watched fellow Republicans refuse to endorse, or even openly oppose, conservative candidates and causes, struggle to respond when those same Republicans demand obeisance to a candidate who they feel denigrated them. Yet, without the unity of the party behind him, McCain will have a difficult time overcoming the combined Obama/Clinton force that will come out of the Democrat Party's nomination. It won't do to take his delegates and dismiss the other half of the party as "fringe." He needs to reach out just as Reagan reached out and made the party stronger.
Senator McCain's speech to CPAC was a good beginning. Now, he needs to follow up with a massive unification campaign to reassure the rest of the party that they are included in his vision.
Locally, it's possible that Republican congressional candidates will get a bit of a lift from the McCain nomination. State legislative candidates will still have to stand on their own, however.