In general, the reasons for voting for Bush the first time would make voting for McCain this time an obvious choice. Similar rhetoric on reduced government, lower taxes, etc. They do belong to the same party, after all.
Bush has not followed through on a lot of the conservative principles. The Republicans took control of the legislative branch (the one that controls money), and Clinton took credit for their work by revelling in the economic prosperity. The Republicans then did what the Democrats had done for so long before - they became drunk and lustful with power, swimming over their heads in fraud, waste, and abuse of that power.
McCain has quietly (and loudly, for that matter) admitted that the Republicans learned from their mistakes. In the inevitable future, when they have the chance to prove they've learned by taking control of the legislative branch again, I will believe them on whole. For the individual of McCain, I believe him. For the individual of his running mate, Gov. Palin, I believe she is a fiscal conservative. Together, with an almost equally split House and Senate (again), I believe they can do for our country what Gingrich accomplished, and then destroyed.
So, I was a supporter of Bush, and hate a great deal of what he's done. I strongly believe that we are far better off from a national security standpoint than we would have been under Gore or Kerry. I believe they would have followed Pres. Clinton's apathetic response to attacks on America and Americans, which would have continued to embolden and strengthen our terrorist enemies.
The reason that the presidential and congressional approval ratings are so historically low, IMO, is exactly the same for each - they're not doing domestically what they were elected to do. Reid and Pelosi do far more damage to our country every day than Bush, thus their institutions' approval ratings are far lower than the executive's. Bush at least is doing the national security job he was elected to do, so his ratings are higher.
So, the answer I would have to give is that I was a supporter, and I support McCain. But, there is absolutely no parallel that you can draw from those two statements together. I drive an American made vehicle, and I support McCain is just as useful a connection.