WASHINGTON — Senate Republicans vying to replace longtime leader Mitch McConnell have been crossing the country to campaign and fundraise for colleagues, making their final arguments before a consequential ballot the week after the presidential election. But their pitches are mostly behind closed doors, and most GOP senators won’t yet say which lawmaker they are backing. [time-brightcove not-tgx=”true”] South Dakota’s John Thune, McConnell’s current No.