DES MOINES  One of the $64,000-questions about Thursday’s Iowa caucuses is how much students from out of state will influence the outcome.

A big argument has been raging here about rules that allow out-of-state students who attend schools in Iowa to vote as long as they are not registered elsewhere. Although presidential campaigns here have been notorious over the years for using out-of-staters to pack rallies and organize, at issue here is their actual participation in the caucuses: some see it as a hijacking of their process, while others see it as a voting rights issue and say that as many people as possible should be encouraged to participate.

The role of students is mainly an issue among Democrats because they tend to draw more young people. Senator Barack Obama of Illinois, whose “change” theme is particularly appealing to young people, has been openly encouraging out-of-state students in Iowa to come back from winter break and caucus.

No one knows how many students will show up or what percent of the final turnout they will make up. But only 124,000 Democrats turned out in 2004, and even if, as predicted, many more turn out Thursday, thousands of out-of-state students here could still have a disproportionate say in the results.