"That's not what President Trump promised," Cassidy, Republican of Louisiana, told CNN. "That's not what Republicans ran on."
Cassidy said he is deeply concerned about the coverage loss under the bill, as depicted by Monday's release of the CBO score, and wants changes to it. He also criticized the White House for trying to discredit the CBO.
"You have to have an umpire, even if the umpire occasionally gets it wrong, because otherwise you are only accepting analysis by people with motivations define certain answers, and so I am very reluctant to disregard what the CBO score is," Cassidy said.
Just days before he was inaugurated, Trump said the Republican health care plan would include "insurance for everybody
." At the time, the comment sent Republican leaders in the Capitol scrambling to explain that Trump really meant the plan would include "insurance access for everybody" -- a big difference.
And Health and Human Services Secretary Tom Price promised this past weekend that "nobody will be worse off financially
" under the Republican health care plan.
But the CBO report found that 14 million people would lose their insurance by 2018 and the number would grow to 24 million over the next decade, driven largely by the ending of the Medicaid expansion included in Obamacare.
The Republican health care bill has run into significant trouble in the House -- with conservatives arguing that it only props up Obamacare -- and faces more hurdles in the Senate, where more moderate Republicans are concerned about cuts to Medicaid.
Cassidy, alongside Republican Sens. Susan Collins, Johnny Isakson and Shelley Moore Capito, introduced what they termed a "comprehensive Obamacare replacement plan
" in January.
Cassidy wasn't the only Republican senator criticizing the bill Tuesday. Sen. Pat Roberts of Kansas told CNN that he would also like to see changes to the House bill to better help low income and rural seniors purchase health care.
When asked if House leadership was open to changes, he responded: "The ones in the room are."
Republican Sen. Jim Inhofe of Oklahoma said he'd like to see "a lot of changes" but overall called the bill a "good start."
When asked if he think it's OK that older Americans could end up paying more, Inhofe responded, "no I don't think that's right."