Most national polls show Americans preferring Democrats over Republicans in the mid-term congressional elections by 10-18 percentage points, though the margin has narrowed in some recent polls. Republicans and Democrats alike are giving extra attention to a a few Senate seats in particular.
Why it matters
The president's party traditionally takes a hit in his first midterm, and Democrats only need 24 House seats and two Senate seats to win majorities in both. But the odds are low that the Senate would change hands, since 10 Democratic senators are up for re-election in states Trump won. It's also worth watching to see if the polls change after the debacle over the government shutdown.