Small margins in passing both the House and Senate bills making it difficult for them to negotiate (even in secret) a compromise bill

My guess is that whether this passes depends a lot on what happens in Massachusetts. From the Hill:

Rep. Anthony Weiner (D-N.Y.) issued a blunt, angry statement on Wednesday, accusing the Senate of conducting negotiations with the House while holding "a gun to our head."

"The House has shown deference to the Senate in this process. But I am tired of hearing how hard it was to get 60 votes in the Senate — getting 218 votes to pass our healthcare bill in the House wasn’t easy," said Weiner, who has taken an increasingly prominent role during the healthcare debate.

"We don’t like negotiating with a gun to our head," he added.

Democratic leaders are working to reconcile the House and Senate bills, particularly a handful of issues — including a tax on "Cadillac plans" and restrictions on abortion funding — that have the two chambers at loggerheads. . . .

Meanwhile the Republicans are sounding a little more optimistic.

House Minority Whip Eric Cantor (R-Va.) proclaimed Wednesday morning after meeting with his conference that "this healthcare bill can be defeated." . . .

"We’re looking at 37 Democrats who are in districts that are particularly upset and vulnerable to the provisions of this healthcare bill," Cantor said, highlighting the key theme to be pursued: "Are they going to be with the people or are they going to be with Pelosi?" . . .