ABC News' Jonathan Karl reports: Senate Democrats – all 60 invited – are heading to the White House tomorrow for a 1:40 p.m. meeting to talk health care. Senate Democrats will huddle at 5:30 p.m. this evening to try to figure to craft a new compromise on health care reform. The closed-door meeting will be held in the Mansfield Room, just off the Senate floor. It’s do-or-die time if they want to get a bill passed by Christmas. Democratic leaders thought they had a compromise that could pass this week, but it crumbled yesterday as Joe Lieberman and Ben Nelson took issue with a central feature of the compromise: allowing Americans 55 to 64 to buy into Medicare. The opposition of Lieberman and Nelson effectively kills the Medicare idea, just like it killed the public option. Now what? Congressional sources tell me the White House is urging Senate Democrats to give-in to Lieberman and to move forward with a scaled-down bill that includes no public option and no Medicare buy-in (although the WH communications director Dan Pfeiffer denies this). The question now is whether the liberals would go along with that in the Senate and, following that, if liberals in the House – many of whom have said they would vote “no” on any bill without a public option – will agree to it. At this point, the focus in on keeping the 60 Democrats in line; if that fails, Democrats may make another run at Republicans Susan Collins and Olympia Snowe, but that would require a new round of negotiations that would be unlikely to be completed by year’s end. And both Snowe and Collins have concerns similar to Lieberman’s. Stay tuned.