The shortlist of Democrats vying to serve as Kamala Harris’ running mate is narrowing down to a few strong contenders, but one unlikely lawmaker seems to be gaining steam, according to a Washington Post analyst. Minnesota Gov. Tim Walz is “the momentum candidate” according to an analysis from senior political reporter Aaron Blake. “Nobody’s stock has risen over the past week as much as Minnesota Gov. Tim Walz, who was previously thought to be something of a dark horse for the job,” Blake writes. “Walz has pushed himself into the conversation with a barrage of media appearances in which he’s pl…