( AP )- 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 in front of partisan audiences than the rival Obama will have to beat first to get to the general election - Hillary Rodham Clinton.
But he also likes to lump the two of them together as co-supporters of the war in Iraq.
"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 during a speech in Denver Wednesday.
The pitch is a timely pivot back to the issue that helped fuel Obama's candidacy - his early opposition to Iraq. Recently the war has become a secondary issue to the declining economy - an issue on which Clinton outdistances Obama in the polls as the more experienced hand to guide the nation though financial turmoil.
Asked about Obama's criticism Friday, McCain said a debate with Obama over the war "will be the difference between victory and surrender."
"Without in any way denigrating or in any way being critical of Senator Obama , who I have great respect for, it's a product of his inexperience," McCain told reporters on his campaign plane. "And we'll be highlighting that. And, inexperience, a lack of knowledge of national security issues can only lead one to the conclusion, that you would have immediate withdrawal from Iraq."
McCain noted that Clinton had a similar position and said he eagerly awaits a one-on-one debate with either of them.
Obama advisers have said privately for months that McCain would be their preferred opponent among all those who sought the GOP nomination. They said a race between Obama , 46, and McCain, 71, would provide the starkest contrast between old vs. new, the future versus the past. It's an argument that Obama also has been using against Clinton, but his campaign feels it would be even stronger against McCain.
Clinton and McCain have worked closely together - one source of their shared reputation for working across party lines on common interests. The two serve on the Armed Services Committee and were drinking buddies at least for a night. The New York Times reported that Clinton challenged McCain to a vodka drinking contest during a congressional trip to Estonia in 2004.
Clinton spokesman Howard Wolfson said Clinton has the strength and experience to take on McCain on national security. And he said it's the New York senator who provides the starker contrast with McCain - because her health care plan would require coverage for everyone while Obama's would not.
"Hillary Clinton will be able to say to John McCain that her health care plan will cover every American while his will leave millions out," Wolfson said. "Because Senator Obama's plan leaves 15 million without health care, that's not a contrast he will be able to make."
Repeatedly during a debate with Clinton Thursday night, Obama brought up McCain as if he were the presumptive GOP nominee. McCain has yet to lock up the race, but a recent win in Florida has made him the front-runner.
"I respect that John McCain, in the first two rounds of Bush tax cuts, said it is irresponsible that we have never before cut taxes at the same time as we're going into war," Obama said. "And somewhere along the line, the `Straight Talk Express' lost some wheels and now he is in favor of extending Bush tax cuts."
Later in the debate, he turned to McCain's position that troops could be in Iraq for the long haul. "When John McCain suggests that we might be there 100 years, that, I think, indicates a profound lack of understanding that we've got a whole host of global threats out there."
While Clinton voted for the war resolution in 2003 and has refused to apologize for it, she has said she would never have given Bush the authority to go to war if she had known he would abuse it. And she says she'll end the war if elected commander in chief.
Obama argued in a press conference Friday that Clinton's war vote makes her a weaker opponent to McCain.
"There is going to be a contest with John McCain potentially - somebody who's been very clear and firm about his position on the war," Obama told reporters. "If we go in there suggesting that it just was not managed well by George Bush, then Senator McCain I think will be able to come back and argue that in fact we have reduced violence in the surge."
"I think it's easier for me to dispute given it's my long-standing belief that it was a strategic error on the part of the Bush administration," Obama said.
He also argued that he would be more electable in a general election matchup against McCain than Clinton.
"I am attracting new voters and independent voters into the process in a way Clinton cannot do," Obama said at his news conference. "I think that'll be particularly important if Senator McCain is the nominee on the Republican side."