Republicans have secured the Senate majority after a series of GOP upsets in key states across the U.S., including in red states such as Indiana and North Dakota.

Between the lines: There are 10 Senate Democrats running for re-election in states that President Trump won. Their challenges explain why Republicans are already projected to keep control of the Senate.

Winning and losing red-state Senate Democrats

Winners

• Sen. Sherrod Brown (D-Ohio)
• Sen. Bob Casey (D-Pa.)
• Sen. Joe Manchin (D- W.Va.)
• Sen. Tammy Baldwin (D-Wis.)
• Sen. Debbie Stabenow (D-Mich.)
• Sen. Jon Tester (D-Mont.)

Losers

• Sen. Joe Donnelly (D-Ind.)
• Former Gov. Phil Bredesen (D-Tenn.)
• Sen. Heidi Heitkamp (D-N.D.)
• Rep. Beto O'Rourke (D-Texas)
• Sen. Claire McCaskill (D-Mo.)

Other Trump state Democrats

• Sen. Bill Nelson (D-Fla.)

Go deeper: The Senate map is trouble for Democrats in 2018