WASHINGTON — Former Senator Alan K. Simpson, the co-chairman of President Obama’s bipartisan commission for reducing the mounting federal debt, figures that with the country in danger of “going to the bow-wows,” he has bigger things to worry about than whether “Rush Babe” and other conservative critics are “babbling into the vapors” that he is not Republican enough for the job.

That is Simpson-speak, recognizable to anyone familiar with Mr. Simpson’s way of treating serious issues with folksy phrases and sometimes stinging humor during 18 years as a senator from Wyoming. But this is no joke: The Republican Party’s insistence that no real Republican would even consider raising taxes is a big reason that many people believe the president’s panel will never agree by December on a bipartisan multiyear plan to narrow the growing gap between spending and revenues.

“Alan Simpson’s a great guy, but he’s not going to bring along Republican votes on Capitol Hill,” said Vin Weber, a former congressman from Minnesota who was part of a younger generation of Reagan-era tax-cutters. “He’s always been a Republican that would be willing to raise taxes, but that’s not where today’s Republican Party is.”

That is likely all the more true of the Republican Party in an election year, especially when it is courting the zealously antitax, small-government Tea Party voters. Still, it is a measure of the building concern about the nation’s fiscal future that some Republicans outside Congress are beginning to challenge the party’s antitax orthodoxy.