a growing number of Republicans are willing to refuse to sign Grover Norquist's anti-tax pledge, or repudiate their signatures, the party may be reaching a tipping point where they "toss aside Americans for Tax Reform’s pledge in order to secure a grand bargain". Norquist has played word games in the past to avoid accusing the Republicans of breaking their pledges, but if you push that type of game far enough you undermine the meaning of the pledge. On the other hand, if you accuse large numbers of Republicans of violating the pledge you are likely to find that they have the collective power to push back, "We have to do what's right for the country," and the legislators would likely have little concern about any effort to punish them - any effort at retaliation would become diluted.
You have to wonder, even if they agree with him in principle, whether a good number of the Republicans who have signed the pledge want to get out from under Norquist's thumb. Once the pledge is broken, it's not clear that Norquist or any similar pledge effort can regain the same level of power or control.