Romney's selection of Ryan, chairman of the House of Representatives Budget Committee, energized the party's core conservative supporters. They love his plan to rein in government spending and shift portions of Medicare, the popular health program for seniors, to a voucher system.
"I accept the calling of my generation to give our children the America that was given to us, with opportunity for the young and security for the old - and I know that we are ready," Ryan said in the excerpts. "Our nominee is sure ready. His whole life has prepared him for this moment - to meet serious challenges in a serious way, without excuses and idle words."
Ryan helps make a battleground of Wisconsin, which has not voted for a Republican presidential candidate since Ronald Reagan in 1984. A Romney victory there could alter the electoral map in a way that could hurt Obama's hopes for re-election.
Democrats have attacked Ryan as a conservative ideologue whose budget proposal would spell the end of Medicare. T he Obama campaign released an online video accusing him of harboring "out-of-step views from a bygone era" that would hurt the middle class, threaten Medicare and undercut women's abortion rights.
They hope to turn the Ryan plan against Romney in states like Florida, which has a large senior population, and Virginia, where thousands of government employees populate the suburbs outside the nation's capital.
The second day of the convention opened with a video tribute to Ron Paul, the libertarian Texas congressman whose disgruntled supporters caused a disruption at the convention on Tuesday in protest of new rules that could hurt similar grassroots movements.
Paul's son Rand, a Kentucky senator, also addressed the convention on Wednesday. Arizona Senator John McCain, the losing 2008 presidential nominee, and Condoleezza Rice, who served as secretary of state under former Republican President George W. Bush, were due to speak.