Justice’s victory all but guarantees Republicans will flip the seat in the ruby-red state currently held by retiring Democratic Sen. Joe Manchin III, giving them a minimum of 50 seats after the election.

Democrats have no room for error: They are defending eight seats Republicans have a shot at winning. ...

Last cycle, untested candidates including talk show host Mehmet Oz and former football player Herschel Walker lost the Senate for Republicans, and Republicans think they have made a huge improvement with wealthy, self-funding candidates in states like Pennsylvania, Montana and Wisconsin who aren’t too extreme to win a general election.