Florida has just had an influx of Puerto Ricans and a sizable population of those to begin with. Guess who completely embezzled the relief funds and a year later the island is still without power? Puerto Ricans are US Citizens and can vote.

ND, WV, and MT are strange in that their senators are popular on their own. Heitcamp is leading by a few points and Manchin will win anyways.

Ohio - wildcard and a swing state, most likely will go blue solely due to the anti-president effect, where the minority party actually gets off their asses and votes.

Missouri - McCaskill is pretty popular and she's being challenged by a complete douchebag republican. She'll squeak through.

Indiana - This one is a huge question mark. You never hear about Donnelly, it basically all depends on the Trump Slump. His challengers aren't known and therefore aren't particularily strong but... it is Indiana.

And now for republican seats:

NV - Heller is toast, dem will take it.
AZ - Hard to gauge, the seat is currently ranked as a tossup. It might flip. We'll have a better view once the damn voting actually starts there.
TX - Judging from how fired up democrat voters are, Cruz has every right to be shitting his pants.
TN - Long shot but considering that a popular former D governor is running for an open seat, it is winnable, moreso than Cruz's seat.
MS Special - This one is an interesting case since special elections in Mississippi are decided by a non-partisan primary followed by a run-off if no one gets above 50%. Technically a democrat could snag the open seat but it'd be a miracle like what happened in AL. Mississippi is also about 40% black, which is a heavy D block.
MS, NE, WY, UT - Basically safe R unless a lot changes.

Another possibility is that McCain kicks the bucket or resigns soon giving us another special election.