I really don’t think that Democrats will cross over in the primaries to vote for Weld or any other Republican primary challenger leading up to the 2020 election, because they will be more focused on the Democrat primary candidates.
Well the Dems will have at least a dozen or more...how many drop out before the primaries I don’t know...
Some might, just to screw with Trump. If he’s going to be reelected, the Republicans will have to unite behind him as tightly as possible. Weld will likely make that more difficult.