By Lauren Fox, Sarah Ferris, Kristen Holmes, CNN (CNN) — Even some of Democratic Sen. John Fetterman’s staffers were caught off guard when they saw him appearing in a video at the Republican midterm convention, according to two sources. But they weren’t exactly surprised. Fetterman has a long history of breaking with his own party, voting for some of Trump’s nominees and backing the president’s military actions in the Middle East. But more than that, the sources said, he is unusually close with the Senate colleague he introduced at the convention: GOP Sen. Dave McCormick. One source involved in the...