NEW: Republicans say they'd happily welcome Sen. John Fetterman to the GOP if he ever decides to leave the Democratic Party. Senate Majority Leader John Thune

NEW: Republicans say they'd happily welcome Sen. John Fetterman to the GOP if he ever decides to leave the Democratic Party. Senate Majority Leader John Thune says the Pennsylvania Democrat would be welcomed into the Republican conference after Fetterman said he'd leave Democrats if the party offic…