DISCLAIMER: I'm not a Bush-hater. I support his vision of a global march to democracy and I think that he's been unfairly lambasted by many over the past seven years.
The lowest points for me, however, during the Bush presidency has involved the issue of checks and balances:
+I was willing to live with a panel that could secretly approve wiretaps of suspected terrorists; I cannot live with Bush's willingness to circumvent even that process.
+I was willing to live with the politically-motivated firing of US attorneys; I cannot accept Bush's defense of his prevaricating then-Attorney General (Alberto Gonzales) and the apparent willingness of the Bush administration to use a clause in the Patriot Act to subvert the traditional requirement of Congressional approval of US attorneys.
Venezuela and Russia have seen have seen dramatic challenges to their democratic institutions in recent weeks. US democracy is much more mature and stable; still, we should therefore be reminded that institutions (e.g. Congress, the Justice Department) depend on citizen awareness and support for their strength and independence.