But this isn’t only a battle between Obama and Republicans. His expansive gun restriction proposal immediately ran up against potentially fatal opposition: Senate Democrats may act only narrowly on Obama’s sweeping proposal, and House Speaker John Boehner says he won’t act unless the Senate does.

This is one fight House Republicans are looking forward to: GOP aides told POLITICO that the president’s push would most likely set up a confrontation with his own party just as he had successfully exploited fractures in the GOP…

Senior Senate aides say Obama will have to do what he has never been willing to do before: lobby Democrats one by one, making the case that a perilous vote is the right thing to do. “[He] should engage with the individual senators who are championing different pieces of this legislation, work to move them forward and also reach out personally to those who may be on the fence to make the case for the policy — and if they believe the politics have changed post-Sandy Hook, why they believe that to be the case,” said a senior Democratic staffer involved in deliberations on the gun issue.

That calculus — a possible Senate thumbs-up coupled with a certain House thumbs-down — used to be enough to deter the president from making an all-out push. Obama’s cautious approach to controversy led his administration to slow-walk action on immigration, climate change, labor rights and gun control during his first term, according to advocates who lobbied the administration on those issues and operatives close to the White House.