Ten Senate seats most likely to flip

Republicans face an uphill road to keeping their Senate majority in the November election.

They must fight to protect 24 GOP-held seats, while the Democrats have to worry about only 10.

Here are the top 10 seats likely to flip, nine of which are held by Republicans.

1. Illinois
2. Wisconsin
3. Florida
4. New Hampshire
5. Pennsylvania
6. Ohio
7. Nevada
8. North Carolina
9. Arizona
10. Missouri