Each person and each situation is different. It's rare if not unique for a powerful member of the House to be chosen as a VP candidate. Just the fact that you are talking about a House member as a possible future president is probably a first for you. Ryan is very intelligent, knowledgeable, articulate and charismatic. He's not Walter Mondale or Dan Quayle, he's a force to be reckoned with and everyone knows it. If Romney/Ryan loses, he'll still be a very prominent member of the House and still have a future as a candidate for National office. If they win, and Romney has a successful 2 term presidency and is still popular in 2020, Ryan will be in a very strong position to succeed him. In either case, everything he has going for him transcends any past patterns regarding VP candidates. In the just concluded Olympics, Usain Bolt and Michael Phelps both accomplished things no one else had ever done. People who are special enough can do that, and I strongly suspect Ryan will demonstrate that same quality as a politician.