Updated at 4:15 p.m. ET
Senate Republicans' health care bill may already be on life support, with four key lawmakers announcing their opposition just hours after the GOP's latest effort to repeal and replace the Affordable Care Act was released.
"Currently, for a variety of reasons, we are not ready to vote for this bill, but we are open to negotiation and obtaining more information before it is brought to the floor," Sens. Rand Paul, R-Ky.; Ted Cruz, R-Texas; Mike Lee, R-Utah; and Ron Johnson, R-Wis., said in a statement Thursday afternoon.