If they want to win, they would need someone not tainted by the current administration. Some conservative democrat that got out before 2008. I can only think of a few that fit that description.
Phil Bredesen, former TN governor, would have a real shot to win if he were their nominee. He served two terms and despite the conservative wave last fall, he probably would have won another. Luckily, the Rats aren’t smart enough to run an experienced businessman, former mayor, and governor who isn’t a radical liberal.