Democratic Senator Claire McCaskill of Missouri concedes defeat at an election-night rally in St. Louis on November 6, 2018. McCaskill lost to Republican challenger Josh Hawley. (Photo by Scott Olson/Getty Images)

(Updated at 8 AM eastern)

(CNSNews.com) – Republican candidates flipped four key Senate seats Tuesday, defeating Democratic incumbents Heidi Heitkamp in North Dakota, Joe Donnelly in Indiana, Claire McCaskill in Missouri, and Bill Nelson in Florida. In Nevada, however, Republicans looked likely to lose what for months has appeared to be the party's most vulnerable Senate seat.

In North Dakota, a state won by President Trump by 35 points in 2016, Republican North Dakota congressman Kevin Cramer defeated the one-term incumbent Heitkamp by nine points.

In Missouri, state attorney general Josh Hawley beat McCaskill by around six points. Trump visited Missouri twice in the closing days of the campaign. In 2016, Trump won the state by 18 points.

In Indiana, Donnelly lost his seat to state lawmakers Mike Braun, by ten points. Trump won Indiana by 20 points in 2016.

In Florida, a state which Trump won by just one point in 2016, Republican Gov. Rick Scott appears to have defeated three-term incumbent Nelson. Scott leads with 50.2 percent, or 34,537 votes, with 100 percent of precincts reporting.

All four of the defeated Democrats voted against Justice Brett Kavanaugh’s Supreme Court nomination last month. (The only Democrat to vote in favor of Kavanaugh, Sen. Joe Manchin of West Virginia, held onto his seat Tuesday, defeating GOP challenger Patrick Morrissey in a state which Trump won by 42 points two years ago.)

In other closely-watched Senate races:

Arizona: Republican Rep. Martha McSally was locked in a tight contest with Democratic Rep. Kyrsten Sinema, for the seat held by outgoing Republican Sen. Jeff Flake. McSally now leads by 0.9 percentage points, or 15,908 votes, over Kyrsten Sinema with 99 percent of precincts reporting.

Montana: Democratic incumbent Sen. Jon Tester was running behind GOP challenger Matt Rosendale. Rosendale had a 0.7 percentage point lead, or 2,993 votes, over Tester with 83 percent of precincts reporting.

New Jersey: Democratic Sen. Robert Menendez, who was tried on corruption charges last year, beat Republican businessman Bob Hugin by ten points.

Nevada: Democrat Jacky Rosen defeated Republican Dean Heller, 50.4% to 45.4%.

Tennessee: Republican Rep. Marsha Blackburn defeated Democratic former governor Phil Bredesen by ten points, to take the GOP seat held by retiring Senate Foreign Relations Committee chairman Sen. Bob Corker.

Texas: Sen. Ted Cruz saw off a challenge from Democrat Beto O’Rourke, beating him by two points, with 97 percent of precincts reporting.