The leadership could deny them the party’s endorsement. They wouldn’t, but they certainly have the ability to do so and have exercised that ability with lots of candidates who tried to run under their banner.
A party can also, via its leaders who are also elected politicians, punish bad behaviour by making sure the elected official doesn’t get prime committee assignments. Here are Manchin’s: Chairman of the Senate Energy and Natural Resources Committee, member of Appropriations, Armed Services, and Veterans’ Affairs. Pretty good for a DINO.
A political party that doesn’t follow through on its convictions sends the wrong message to those it counts as its members. The DNC leadership, especially where it overlaps with elected office, is weak and wishy-washy.
