Obama uses McCain's lead in Republican primary as argument for his own candidacy

Democratic Sen. Barack Obama sees one of the best arguments for his presidential candidacy in the rise of Republican Sen. John McCain.

McCain has become Obama's favorite punching bag, an easier mark before partisan audiences than the rival Obama will have to beat first to get to the general election, Sen. Hillary Rodham Clinton. He also likes to lump the two of them together as co-supporters of the Iraq war.

"It is time for new leadership that understands the way to win a debate with John McCain or any Republican who is nominated is not by nominating someone who agreed with him on voting for the war in Iraq," Obama said Wednesday during a speech …