No, not the one about second-term presidents never recovering if their approval sinks; I saw that again today, but I've already handled that one.
It's this one (my emphasis):
“I don’t know where the breakdown occurred on that, but it’s Obama’s ‘no new taxes’ moment,” the official said, referring to the broken promise that is widely seen as having cost President George H.W. Bush a second term.Hogwash! What cost George H.W. Bush a second term was a poorly timed recession. That's all.
Bush breaking his tax pledge was a story in June through October 1990. Look at his approval ratings: it's hard to make much of it. In particular, this all happened before the Gulf War, which relegated it to ancient history. One can argue that it hurt Bush in the long run by destroying trust in him, but that certainly didn't seem to have any effect at all in spring 1991. Only when the economy turned south did his approval ratings follow.
I suspect that for the neutral press, this is a close relative of the equally untrue myth that Ross Perot cost Bush the election. Why? Because after three consecutive solid Republican victories, by 1992 most Republicans believed the myth of a GOP "electoral lock" and therefore were open to bogus explanations of something which actually didn't need much explanation at all beyond the obvious one that incumbent presidents usually lose re-election if there's a recession in the second half of their term. What distinguishes this one, I'm sure, is that a faction of the Republican Party is intensely interested in convincing everyone that higher taxes ruined Bush's presidency, while pretty much no one else cares.
At any rate, at best breaking the pledge was a very minor factor in the 1992 election, and most likely it had no effect at all. Moreover, to the extent that it hurt at all, it may well have been because of how central, high-profile, and specific the pledge was in Bush's 1988 campaign. I'd guess it's easily in the top 1% of all campaign pledges ever if all those factors are combined, and pretty high up there as far as how high-profile and absolute the breaking of it was. Really, however, it likely made no difference at all in 1992.