A new SurveyUSA poll, conducted for Roll Call, shows that the usually-Republican Illinois district of former Speaker Dennis Hastert may well switch to the Democrats in this Saturday's special election.

The poll showed Democratic candidate Bill Foster, a businessman and scientist, ahead of Republican dairy magnate Jim Oberweis by a 52%-47% margin.

The district voted 55%-44% for President Bush in 2004, but Foster has been helped by such diverse factors as Oberweis' past failed campaigns for governor and senator, the endorsement of the conservative Chicago Tribune, and this ad starring Barack Obama: