Two days before the Nevada caucuses, Senator Dean Heller (R.,NV) has thrown his weight behind Marco Rubio for president. Heller, previously a Jeb Bush supporter, announced his endorsement this morning on Twitter. The move comes mere hours after Bush's exit from the race on Saturday evening. Marco Rubio "is the next generation of conservative leadership, and I am proud to offer my full support," Heller tweeted. "Marco understands Nevada, he grew up here -- I look forward to campaigning with him today," he added. Heller's imprimatur could help Rubio thread the needle with crucial pockets of the Silver State electorate....