GOP mega-donor Wall Street billionaire Paul Singer is actively fundraising for Sen. Marco Rubio (R-FL), several sources have confirmed for Breitbart News. One, a source close to Rubio and Rubio’s presidential campaign, confirmed it to Breitbart News’ Sarah Rumpf—who is in Miami at Rubio’s campaign rollout. Others, including sources close to Singer, have also confirmed it to Breitbart News.