Tensions inside the Republican Party about a proposal to defund Obamacare reached a new level Friday when Sen. Tom Coburn, R-Okla., a lawmaker with unsurpassed credibility in the field of cutting federal spending and limiting the size of government, called the defunding plan “dishonest” and “hype.”

In a phone interview from his home state of Oklahoma, Coburn slammed a dozen fellow Republican senators who have signed a pledge not to vote for any continuing resolution or appropriations bill that funds Obamacare, which is set to go fully into effect on January 1, 2014. “I’d love to defund it,” said Coburn, a physician who has opposed the president’s national health care scheme from the beginning. “I’d be leading the charge if I thought this would work. But it will not work.” (For details on the problems with the defunding plan, see here.)