The polls in Illinois have closed. Early exit polls show Mitt Romney with a 10 point lead. He came into the day with a 14 point lead over Rick Santorum. Considering the margins of error, a low double digit lead isn’t a shock.
Fox has county-by-county results here.
The usual dynamics seem to apply to Illinois: Romney does well in the urban and collar counties, Santorum does well in more rural areas. If that holds, Romney should take Illinois.
Update: Fox News projects that Mitt Romney has won Illinois. More to come.