Unofficial results in Missouri show McCain winning by about 4,900 votes. There are about 6,300 provisional ballots statewide that county officials are still reviewing. Counties must send final results to the state by Nov. 18.So, yes, there are believed to be more provisional ballots outstanding than the margin between John McCain and Barack Obama. Obama could do quite well among these provisional ballots ... provisional ballots almost always tend to favor Democrats, and a large fraction of Missouri's provisionals are reportedly in St. Louis, Obama's strongest part of the state.
Even if Obama were to win 80 percent of the provisionals, however -- which seems exceptionally optimistic -- he still would net only 3,780 votes, leaving him about 1,000 shy of McCain. Moreover, some provisional ballots are in fact illegitimate, cast by voters who are not properly registered, etc. The rules of thumb I have seen are that somewhere between one-half and two-thirds of provisional ballots usually hold up upon review. A more realistic scenario then is that two-thirds of the provisionals are counted and two-thirds of those go to Obama, in which case Obama would net about 1,400 votes, not nearly enough to close his gap with McCain.
In other words, in order for Obama to win Missouri, he'll need some source of votes apart from the provisional ballots. Mistakes are sometimes made in the vote-counting process, and Missouri doesn't finalize its count until Tuesday, so this is always possible. There's just no reason to think it's especially likely ... maybe John McCain is a 99% favorite to win Missouri but not a 99.9% favorite, and the networks usually want more like 99.9% certainty before they call a state.
Now, Obama does have the right to request a recount in Missouri, provided that the margin is less than 1 point, which it obviously will be. But Claire McCaskill has said that he sees no point in doing so, and besides that, a margin of a few thousand votes is exponentially more difficult to make up in a recount (i.e. it's nearly impossible) than a margin of a few hundred votes, like we have in Minnesota.
Missouri may be having trouble coping with the fact that it's no longer the king of bellwether states, but in all likelihood it's just going to have to deal with ceding its title to Ohio or whatever.