What about dropout candidates?

John Edwards, Fred Thompson, Rudy Giuliani and Bill Richardson have recently jumped from the presidential race, but their names will still appear as an option on today's ballots.

Election experts say voters should be aware that voting for those candidates will have no impact on getting them elected.

"You can vote for them just to indicate who you really like even though they are out of the race, but that vote is not going to count for allocation of any delegates," said Ron Michaelson, a political science professor at the University of Illinois at Springfield and the former director of the Illinois State Board of Elections.

While votes get all the attention in the election, it is really delegates that matter to the candidate. The contender with the most delegates -- people pledged to vote for him or her at the party's summer convention -- wins the nomination.

On the Democratic side, if a candidate doesn't acquire at least 15 percent of the vote in a congressional district, then any votes he or she did get are thrown out.

The remaining votes are reapportioned and the remaining candidates get a portion of delegates equal to their vote percentage.

So, for Edwards or Richardson to win delegates, they would have to get more than 15 percent of the vote in a congressional district.

Reaching that threshold is very unlikely since they have dropped out of the race.

On the Republican side, the candidate with the most votes in a congressional district wins all the delegates. The other contenders do not get any delegates.

So, for Thompson or Giuliani to pick up any delegates, they would have to win an entire district -- another unlikely prospect.

"I hate to say a vote won't count," Michaelson said. "But it won't be translated into delegates, which is what matters most in the primary."