(CNN)Sen. Lindsey Graham vowed Monday to "press on" in a bid to pass an apparently doomed Obamacare replacement bill he's sponsoring, calling the proposal a "damn good idea."

"We are going to press on. It's OK to vote. It's OK to fall short, if you do, for an idea that you believe in," Graham told CNN's Jake Tapper and Dana Bash at town hall debate in Washington.

But Democratic Sen. Bernie Sanders blasted the Republican approach, which must pass by an end-of-the-month deadline or go down to defeat as a "disaster," and pushed his own long-term plan for a universal health care system.

Graham and fellow Republican Sen. Bill Cassidy are facing off against Sanders and Democratic Sen. Amy Klobuchar in the debate, with their measure appearing all-but-doomed after a third Republican, Sen. Susan Collins of Maine, came out against it.