There's a myriad of reasons to not want another Bush in the White House. They have a mixed record of conservatism at best. I'd give the Bushes a combined rating of D- at best. They did not embody conservatism, but rather establishment-ism. And if the GOP is not a conservative party, then why does it even exist? We've already got a progressive liberal party, There's no need for a somewhat less progressive and less liberal party. Furthermore, no name will stir the liberal base the way the name Bush will do.
I doubt that conservative voters will rally around Jeb Bush the way the Republican establishment appears to be doing. The problem with the counterweight on the actual conservative side is a split vote among many candidates.
In short, a successful Bush run, is yet another recipe for defeat. Romney, McCain, Bush, Dole, Bush have been a list of elites with only 2 wins in 6 tries since 1992, and one win was without a popular vote win to boot. In fact the other win was based on war time support. The establishment appears to be running on fear of being losing and it proves to be the wrong strategy most every time.
Not only is an establishment, liberal Republican bad, another Bush is the worst possible name of the lot. Truly, truly a bad idea.