Marc Elias, the Democratic lawyer and power broker, was having a big day. His by turns earnest, exultant and swaggering Twitter presence had pushed him over a milestone: “400k,” he posted earlier this month, accompanied by an emoji wearing a party hat and blowing a streamer. Elias, 51, who rose to prominence a dozen years ago in the Minnesota recount that sent Al Franken to the United States Senate, became over the past two years a treasured backstop for Democrats worried that voter suppression would lift President Trump to a second term. He leveraged that following to build a voting-rights group, Democracy Docket, and a public following, and a reputation that has only swelled this fall, as he racked up 59 victories in the 60 cases he has filed since the Nov. 7 election.