Obama introduces Biden as his running mate

Saturday, August 23, 2008 | 4:18 p.m. CDT; updated 4:30 p.m. CDT, Saturday, August 23, 2008

SPRINGFIELD, Ill. — Barack Obama introduced Sen. Joe Biden of Delaware on Saturday as a man "ready to step in and be president," and the newly minted running mate quickly turned his campaign debut into a slashing attack on Republicans seeking four more years in the White House.