THE BISHOPS’ BLESSING…. For center-right Democrats in the House, weighing whether or not to support a once-in-a-generation chance at passing health care reform, an endorsement from the AARP didn’t much matter. An endorsement from the AMA didn’t matter either. Support from the American Nurses Association and American Cancer Association barely raised an eyebrow.

But the U.S. Conference of Catholic Bishops seems to make quite a difference.

House leaders have won the backing of the nation’s Catholic bishops for health reform, a critical last-minute boost that could give the bill enough momentum — and enough votes — for passage as early as Saturday. […]

“Passing this amendment allows the House to meet our criteria of preserving the existing protections against abortion funding in the new legislation,” the bishops wrote in a letter to individual members. “Most importantly, it will ensure that no government funds will be used for abortion or health plans which include abortion.”

It’s another bitter pill for liberal Democrats but party leaders are gambling that the amendment will be just the breakthrough they need to secure a majority. And in fact, most Democratic advocates of abortion rights appear likely to swallow hard and vote for a health care overhaul anyway.

“I don’t believe any of us believe we can hold up what we’ve been fighting for … and that’s health care,” said Rep. Louise Slaughter (D-N.Y.).

Asked whether her allies in the pro-choice movement would support the bill with the Stupak language, Speaker Nancy Pelosi offered a one-word answer: “Yes.”

As for the vote on the Stupak/Ellsworth measure, Greg Sargent reports this morning that most Republicans are likely to join the Dems who oppose abortion rights: “A senior GOP aide tells me only a handful of Republicans will oppose the amendment, and a majority will support it. So if the 40 or so anti-abortion Dems expected to support it don’t change their position, it’ll almost certainly pass.”

In about 20 minutes, President Obama is scheduled to arrive on the Hill for some additional lobbying, reminding Democrats about the historic opportunity they’ll have today.

This is not only relevant in pulling together some lawmakers who remain on the fence, it also reinforces the significance of the day — if the leadership planned to push the vote off until tomorrow or next week, they probably wouldn’t have the president making a final push.

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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.