What exactly is a “centrist Democrat?”
A Democrat who markets himself or herself as a fiscal and/or social comservative in order to get elected in a center-right district with weak or compromised Republican candidates. That’s what a “centrist Democrat” is. They’ll horsetrade for cover on highly controversial votes in order to maintain viability back home, but will toe the line reliably when necessary.
Not mich different from a RINO, really. They just play for the other team.