Tom Williams/CQ Roll Call via AP Images From left, Senators. Mark Warner, Elizabeth Warren, Bernie Sanders, and Amy Klobuchar, leave the Senate Democratic Caucus leadership elections in the Capitol, November 16, 2016. E ven as Democrats brace themselves for the inauguration of Donald Trump as the nation's 45th president, they are focused on 2020 and on who can help them recapture the White House. No Democrat has yet declared any interest in running for president, but the successful candidate for 2020 will have to be somebody who has a record of accomplishment, played a key leadership role in opposing Trump’s policy initiatives, can win Democratic primaries that will be dominated by liberals, turn out black, Latino, young, and low-income voters, and win back some white, working-class, swing-state voters who voted for Trump. One has to assume that the next Democratic candidate will by facing off with Trump, but it is possible that he won't want to run again or that he will be dethroned...