But the margin for error is slim. Assuming all Democrats vote against the legislation, GOP leaders cannot afford more than 21 defections in the House and two in the Senate.

The Hill's Whip List: Where Republicans stand on ObamaCare repeal plan | TheHill

"two in the Senate"....so far, Rand Paul is out. Figuring the same motivation (wanting another run at the Presidency), throw in Marco Rubio and Ted Cruz and maybe even Mike Lee.

That's four already.

BTW, no Democrat will support Ryan in the House or McConnell in the Senate.....despite the fevered fantasies of the Right.