Well, they want his vote for the next year or two, but then they can afford to throw him away, the way they did with Jumping Jim Jeffords.
Every car in Vermont seemed to have a bumper sticker praising Jeffords for switching parties. They loved it. But when election time came around again, he was out on his ear.
As I recall, the popular Jeffords never ran as a Democrat. Bernie Sanders took the seat instead.