It's something of a surprise. While Ryan was on all the lists when it came time to speculate about Romney's likely choice, the conventional wisdom had been that it was more likely to be someone such as Ohio Sen. Rob Portman or Florida Sen. Marco Rubio.

Ryan comes from a competitive state with just 10 Electoral College votes. Ohio's 18 and Florida's 29 are much more valuable prizes.

But Ryan is a favorite of conservatives across the nation for his tough talk about tax cuts, spending cuts and fiscal discipline.