FILE - House Budget Committee Chairman Rep. Paul Ryan, R-Wis. introduces Republican presidential candidate, former Massachusetts Gov. Mitt Romney before Romney spoke at the Grain Exchange in Milwaukee, in this April 3, 2012 file photo. Romney has picked Wisconsin congressman Paul Ryan to be his running mate, according to a Republican with knowledge of the development. They will appear together Saturday Aug. 11, 2012 in Norfolk, Va., at the start of a four-state bus tour to introduce the newly minted GOP ticket to the nation. (AP Photo/M. Spencer Green, File)
NORFOLK, Va. (AP) --The candidate made his announcement to supporters via a phone app, saying "Mitt's Choice for VP is Paul Ryan."
The GOP ticket is kicking off a four-day bus tour today that will take them to as many battleground states.
At 42, Ryan is a generation younger than the 65-year-old Romney and the seven-term Wisconsin congressman is a favorite of some conservatives.
Ryan heads the House Budget Committee and is author of a House-passed budget that would slash federal spending and overhaul entitlement programs like Social Security and Medicare.