With today’s launch of the “Rundown,” we wanted to unveil our list of the Top 10 Senate seats that could switch parties in November — a list we’ll continue to update between now and Election Day 2018. No. 1 means most likely to flip. A reminder: Democrats need to pick up a net of two seats to gain control of the U.S. Senate.

1. Nevada (R): A tough GOP primary + a state Hillary Clinton won in 2016 + a Dem challenger facing minimal opposition = Sen. Dean Heller, R-Nevada, being the most endangered Senate incumbent of 2018.
2. North Dakota (D): Republicans are divided over whether this race or the Senate contest in Missouri is their best pick-up opportunity now that GOP Rep. Kevin Cramer has decided to challenge incumbent Democratic Sen. Heidi Heitkamp. But the tiebreaker goes to North Dakota, given that Trump got 63 percent of the vote there in 2016 versus 56 percent in Missouri.
3. Arizona (R): This race remains the most fascinating Senate contest of 2018. There’s a competitive GOP primary to replace retiring Sen. Jeff Flake, the potential of a November showdown between two female candidates (Democrat Kyrsten Sinema vs. Republicans Martha McSally or Kelli Ward) and, of course, the presence of Joe Arpaio.
4. Missouri (D): In what looks like a 50-50 race between incumbent Democratic incumbent Claire McCaskill and Republican Josh Hawley, the scandal surrounding Republican Gov. Eric Greitens doesn’t help the GOP.
5. West Virginia (D): Who would you rather be: West Virginia’s most famous politician (Democrat Joe Manchin) running in a state where Trump got 68 percent of the vote in 2016, or a lesser-known Dem senator (Joe Donnelly) running in a state where Trump got 56 percent? Because Democrats have had more recent success in Indiana (see Obama in 2008), we’ll go with Donnelly. But we expect these states to switch back and forth between now and November.
6. Indiana (D): See above.
7. Wisconsin (D): It looks like it will be a long — and expensive — GOP primary between Republicans Leah Vukmir and Kevin Nicholson, with outside groups pummeling incumbent Democratic Sen. Tammy Baldwin in the meantime.
8. Florida (D): We could very well move up this race if/when Republican Gov. Rick Scott — and his millions — jump into the contest to challenge Democratic incumbent Sen. Bill Nelson. Scott’s shift on guns after the Parkland shooting has been striking.
9. Tennessee (R): Republicans caught a break when retiring GOP Sen. Bob Corker decided not to re-enter this race, which would could have produced a bitter primary between Corker and Rep. Marsha Blackburn. But given the national environment and the big-name Democratic candidate (former Gov. Phil Bredesen), this race remains worth watching.
10. Ohio (D): One of the key questions of this 2018 season is if Democrats — in the Senate and gubernatorial contests — can get their groove back in Ohio after their shellacking there in 2016. Brown seems to be in as good of a position as Democrats could have hoped at the beginning of this cycle. But like Tennessee, this race is worth watching.

Other Senate races to watch (in alphabetical order): Minnesota (Tina Smith seat), Mississippi, Montana, Nebraska, Pennsylvania, Texas