Whatever they might be called, there are still some number of voters who will move their presidential vote from one party to the other during different elections. I think they are around 20% to 30% of the electorate. The rest are pretty firmly to the left or right and probably nothing will cause them to vote for the other party, though there are things that will cause some of them to stay at home.
That's the first piece of politics that Thomas Jefferson proved as his new Republican/Democratic party crushed the Federalists out of existence.
His claim to fame in raw gutter politics was GET OUT THE VOTE ~ get your people to vote for your party people ~