Either in their State party conventions or through appointment by their State party leaders.
It is possible that one of the more moderate states or a state that leande Dem but went * COULD, in theory have a more moderate representaion in the Electoral College. The chances would be better if fraud was actually proven in a swing state, and at a level that would prove that, say, Kerry actually won. But it's highly highly doubtful. Some states have laws that REQUIRE them to vote for the candidate with the most popular vote...Ohio being one of them and Florida another...gee, why do you think the GOP targeted them?
From
http://www.archives.gov/federal_register/electoral_college/faq.html#popular :
"The Supreme Court has held that the Constitution does not require that electors be completely free to act as they choose and therefore, political parties may extract pledges from electors to vote for the parties' nominees. Some State laws provide that so-called "faithless electors" may be subject to fines or may be disqualified for casting an invalid vote and be replaced by a substitute elector. The Supreme Court has not specifically ruled on the question of whether pledges and penalties for failure to vote as pledged may be enforced under the Constitution. No elector has ever been prosecuted for failing to vote as pledged."
Although....from
http://www.archives.gov/federal_register/electoral_college/faq.html#tieQ. "What would happen if two candidates tied in a State's popular vote, or there was a dispute as to the winner?
A. A tie is a statistically remote possibility even in smaller States. But if a State's popular vote were to come out as a tie between candidates, State law would govern as to what procedure would be followed in breaking the tie. A tie would not be known of until late November or early December, after a recount and after the Secretary of State had certified the election results. Federal law would allow a State to hold a run-off election.
A very close finish could also result in a run-off election or legal action to decide the winner. Under Federal law (3 U.S.C. section 5), State law governs on this issue, and would be conclusive in determining the selection of Electors. The law provides that if States have laws to determine controversies or contests as to the selection of Electors, those determinations must be completed six days prior to the day the Electors meet."
So if we could enough evindence to either get a recount...a continuation of the count...or anything like that, it might be enough to swing the popular vote...in whicn case the state would HAVE to cast it's votes for Kerry.