>>A populist is a person who is up for whatever the crowd wants today.<<
OK, now I know what you mean by that term. I think your meaning is different from the usual meaning, which is one who opposes the “elites.”
That's certainly a connotation of the word "populist" - for example, the class warfare so integral to populist political nostrums.
Both John Edwards (a left-wing populist) and Pat Buchanan (a right-wing populist) bitch and moan about free markets and "CEO pay" and NAFTA and "the elites."
And, of course, one of them is a millionaire trial lawyer and the other is a millionaire Beltway journalist.