A major conservative organization dropped its opposition to the Republican healthcare bill, on the same day House Speaker Paul Ryan, R-Wis., hopes to push the bill through on the thinnest of margins.

"With its support of the Meadows-MacArthur amendment, the Club for Growth officially withdraws its opposition to HR 1628," the Club for Growth wrote in a message to congressional offices Thursday morning.

Ryan struggled to rally the votes for the legislation over the last several weeks, as a coalition of moderates and conservatives opposed the bill for conflicting reasons. That logjam broke when House Freedom Caucus Chairman Mark Meadows, R-N.C., and Rep. Tom MacArthur, R-N.J., negotiated an amendment to the legislation that would give states the power to opt out of Obamacare regulations. That compromise convinced the most fiery conservative groups to relent in their opposition to the bill.

"To be clear, this is not full repeal and it is not what Republicans campaigned on or outlined in the Better Way agenda," said Heritage Action CEO Mike Needham. "The amendment does, however, represent important progress in what has been a disastrous process. Given the extreme divides in the Republican Party, allowing Texas and South Carolina to make different decisions on health insurance regulations than New York and New Jersey may be the only way forward."

The Club for Growth operates one of the most formidable super PACs in conservative politics, so their announcement that they are not demanding lawmakers vote against the bill might alleviate fears that supporters of the bill will draw a well-funded primary challenge.