I think breaking his "No New Taxes," pledge is what doom Bush.
Not surprising, left leaners trend towards more taxation so "no new taxes" is a bit of an insult to them. A slight leftward lean is all that differentiates Democrats from Republicans and the "independents" are about as equally divided ideologically as their partisan counterparts.
If the failure to uphold a promise of "no new taxes" was a trigger issue among right leaning independents then they would be pissed off enough to come out in slightly higher numbers against the failing executive.
Which they did. Back in those days independents weren't broke down into independents lean Democratic, independents lean Republican and pure or true independents with no leans as Gallup does today.
So we'll have to take independents as a whole for 1988 and 1992. Bush won independents 57-43 over Dukakis, but lost them to Bill Clinton in 1992 42-28 with Perot getting 30% of the independent vote. Putting Perot aside, Bush won independents by 14 points in 1988, lost them by 14 points in 1992 a swing of 28 points. That does show you how finicky independents can be. How huge swings among the independent voter can take place in a span of just four years. That can happen in two if we look at 2016 where Trump won independents 46-42 a plus 4 to 2018 when independents voted for the democratic congressional candidates 54-42 over the Republicans. That a plus 4 to a minus 12 or a swing of 16 points in just 2 years. These swings can be huge and they can decide elections.
I think one needs to remember that independents aren't loyal to either party and they don't adopt either party's agenda. If they did, they wouldn't be independents. They can also change their votes on a whim. It doesn't take much.
It's high past time that we start electing Americans to congress and the presidency who put America first instead of their political party. For way too long we have been electing Republicans and Democrats who happen to be Americans instead of Americans who happen to be Republicans and Democrats.