Transcript for Jimmy Kimmel takes on the architect of the new Republican health care bill
turning over responsibility to the states. But it is running into a lot of opposition tonight, including from late night TV host Jimmy Kimmel, making his personal story a political one. ABC's Mary Bruce with the tally, Republican senators can only afford two "No" votes. Reporter: Tonight, Jimmy Kimmel is taking on the architect of the new Republican health care bill. And this guy, bill Cassidy, just lied right to my face. Reporter: Last spring, Kimmel shared the emotional story of his infant son's heart condition. No parent should ever have to decide if they can afford to save their child's life. It just shouldn't happen. Reporter: In response, senator Cassidy promised he would defend protections for people with pre-existing conditions. Bhu now, Kimmel says he's not living up to his word. You can promise those people with pre-existing conditions that they will not be charged more, they will not be discriminated against? Absolutely. It's in the legislation. Reporter: But experts tell us there's no guarantee. In the new bill, states could allow insurers to charge more to people with some pre-existing conditions. States still have to provide adequate and affordable coverage, but those terms are not defined or enforced. Optional pre-existing condition? Reporter: The budget office is set to release a report next week, outlining how much the bill costs, but not how many Americans could stand to lose coverage. For that, they need more time. Mary Bruce with us live tonight. Mary, as you point out, we're still waiting for the cbo score, which would estimate how many fewer Americans would be insured. In the meantime, we know that Republicans can only afford to lose two votes. Four key senators tonight, Rand Paul, John McCain, Susan Collins, Lisa murkowski, they could be pivotal here. What do you know? Reporter: David, here's the state of play. Paul tells me he's a no. Collins is leaning now. Murkowski says she's studying the bill. And McCain won't say where he stands. Republicans do not have the votes yet. But they intend to hold a vote next week. David? Mary Bruce live on the hill again tonight. Thank you, Mary.
This transcript has been automatically generated and may not be 100% accurate.