I would define a moderate as someone who is near to the center of the whole nation, not just their party.

Back in the 70's, the line between the major parties was far blurrier than today. Conservative Democrats and Liberal Republicans were significant voting blocs. Someone near the center of Democrats would be a bit to the left of someone near the center of Republicans, but both would be moderates on a national scale.

The firming up of Republican=Conservative+Right and Democrat=Liberal+Left didn't happen until after 1980.

The party tents have shrunk and the overlap has diminished. Naturally, the party centers have moved apart from each other. That JB has moved with his party is what makes him "squishy." I don't use that word as a bad thing; just as an opposite to those politicians that don't change any of their stances as the world changes around them. There's plenty of room for both in the system.