Former New York City Mayor Rudy Giuliani has signed on as an adviser to a political group that is being set up to promote President-elect Donald Trump’s ambitious agenda.In an interview on Thursday evening, Giuliani, a close Trump ally who had once hoped to become secretary of state, said he had decided to play an active role in boosting the newly formed Great America Alliance, a 501(c)(4) nonprofit, to help advance Trump’s policy goals through what is expected to be a wall of Democratic opposition.“Winning the election is one thing.