A number of Republicans are playing down anti-tax pledges they signed with Norquist's group. "We take an oath to uphold the Constitution" and "that trumps any and every consideration," said Cornyn.
"I didn't know I was signing a marriage vow," said Representative Mike Simpson of Idaho, one of 40 House Republicans who recently signed a letter signaling willingness to raise taxes as part of a major deficit-cutting deal.
Senator Lamar Alexander, the chamber's third-ranking Republican, said he saw a sign of shifting opinion when three of the supercommittee Republican members -- Toomey, Rob Portman of Ohio, Arizona's Jon Kyl -- briefed Senate colleagues on their plan and no one complained.
"For Pat Toomey and Portman and Kyl to come in and tell a whole roomful of Republicans that 'we've put $250 billion of tax increases on the table' and not get a murmur of dissent is remarkable," said Alexander.
Senator Saxby Chambliss, a Georgia Republican, said his party's lawmakers should consider bigger tax increases if it would lead to a larger debt-reduction deal, because the political price they'll pay will essentially be the same.
"You're going to be criticized by the same people irrespective of what the number is," said Chambliss.