The top Senate seats most likely to flip

Senate Republicans believe they are on the cusp of increasing their majority in the midterm elections despite historic headwinds that seem likely to cost the GOP control of the House.

Republicans believe they have growing momentum to pick up seats in North Dakota, Missouri and Indiana, while races in Montana and Florida remain tight.

The GOP is feeling more bullish about not losing any of their own incumbents up for reelection, a significant turn-around from earlier in the cycle when Nevada Sen. Dean Heller was seen as possibly the most endangered Senate incumbent standing.

Surprises are still possible on Tuesday in a quickly changing environment.

Here's a look at the Senate seats more likely to flip: