First, I like the pick, I think Paul Ryan is the most intelligent person in politics that is currently in DC, but Romney made a serious error, he announced his pick too soon.
As everyone here realizes, nominees often get a significant boost after their party's convention. People watched the 08 convention because nobody knew who McCain picked as his running mate until the Convention. Bush didn't announce his running mate until the Convention back in 2000 either. It is a way to get people to watch the convention, a suspense builder as it were.
Regardless of what people say about McCain's pick for VP, I think that he made a brilliant choice, but we lost in 08 due to McCain's campaign team being a bunch of morons.
I understand one of the possible reasons that he didn't pick Rubio (specifically the United States Senate seat). Granted Ryan has an important position in the House of Representatives, but we have a pretty large majority in the House.
I am sincerely glad he didn't pick Christie whom is rather liberal on social issues, also glad Pawlenty wasn't picked (whom is a total flop), etc. He picked about the only person in Washington currently that can do basic math, Ryan will pulverise Biden in a debate.
My problem is that Romney announced his choice way too early.