WATCH BOTH CHAMBERS…. In general, it seems most of the talk about the fate of health care reform focuses on the Senate. To be sure, that makes some sense — in light of Republicans’ refusal to allow the Senate to vote, up or down, on key bills, it’s the chamber that seems more likely to kill legislation.

With reconciliation now on the front-burner, the question becomes whether enough Senate Democrats can stick together and secure a majority.

But let’s not forget that the House, which would be required to approve the Senate bill and a legislative fix, is facing a heavy-lift, too. The assumption that the House will be far less of a problem for reform proponents may prove to be wrong.

House Speaker Nancy Pelosi, D-Calif., has signaled to the White House that it’s unclear if there are enough votes in the House to pass the Senate bill.

The House version passed in November by a vote of 220-215, but since then three “yea” votes have vanished: Rep. Robert Wexler, D-Florida, retired; Rep. John Murtha, D-Penn., passed away; and Rep. Anh “Joseph” Cao, R-Louisiana, has signaled he will not vote for the final bill.

That puts Pelosi in a starting-off point of 217 votes which is a majority of the current 433-member House of Representatives, but is also a tough starting line…. Pelosi believes passing the bill is “possibly doable,” the senior White House official said. “But she may ultimately decide the math is impossible.”

There are 255 House Dems, but among them are plenty of opponents of their party’s reform efforts. There are Blue Dogs, who may or may not be more inclined to vote for a more moderate bill along the lines of the Senate plan, and there are liberals like Dennis Kucinich (D-Ohio) who’ve said they’ll oppose Democratic plans that fall short of single-payer.

Moving forward, then, reform advocates will have plenty of phone calls to make — to both chambers — and the burden will be on President Obama and congressional leaders to pressure rank-and-file members to get this done. The pitch to Democratic members is probably pretty obvious — I seem to recall a certain strategy memo a blogger wrote last month — but antsy lawmakers, some of whom foolishly think failure is less scary than success, may need some reminders.

The alternative is the death of health care reform for another generation.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.