Obama's rivals, especially Clinton, don't want voters making that leap of faith.
They pounce on Obama's every gaffe (i.e. referring to U.S. lives lost in Iraq as ''wasted''), exploit any misstatement (saying 10,000 people died in a tornado that actually killed 12) and call Obama naive for stating the obvious (nuclear arms against Afghanistan and Pakistan are not an option).
The first-term Illinois senator hasn't helped his case with a string of shaky debate appearances, a streak he ended Sunday with a strong performance in Iowa as his more experienced rivals took aim.
Asked whether Obama was ready to be president, white-haired Sen. Chris Dodd of Connecticut replied, ''You're not going to have time in January of '09 to get ready for this job.''
Obama hopes he still has time to win the job.
''I think it's fair that I've got to earn the confidence of the electorate,'' Obama told AP. ''What we've tried to do over the course of the last six months is make the case for change, and the American people are desperately hungry for change. The next four or five or six months will involve me making the case that not only am I the most effective change agent but I'm also equipped with the experience and judgment to be the next commander in chief.''
On the campaign trail, Obama gently reminds voters that Clinton and Edwards are not so experienced: She is a second-term senator who has never run a government or business. Edwards served one term in the Senate.
''I've been in public office longer than Hillary Clinton has,'' he said Monday, counting his seven years in the state Senate and not counting Clinton's three decades in public life with her husband. ''I've been in public office longer than John Edwards has.''
Obama could close the stature gap by producing more detailed plans for lowering health care costs, taming the federal debt, resolving the Iraq war and addressing other issues. Edwards, so far, has the edge on the so-called policy primary.
It would help had Obama spent more time overseas. Clinton has made several trips to Iraq and other foreign spots.
For now, Obama seems to be relying on a calm, comfortable campaign demeanor to a send the signal that he is a man in control. In a word, safe.
He has a relatively thin resume, but it's not without accomplishments _ working across party lines to change ethics, death penalty and racial profiling laws in Illinois. Ethics and nuclear proliferation are his signature issues in the Senate.
''I've got a track record, not only in the state legislature but in Washington for taking on tough issues and getting something done,'' he said.
''I want to make sure that during the course of these next four or five months we talk about experience and judgment, not just in the ways that Washington has defined it but in the ways the people outside Washington understand it,'' Obama said.
That assumes he can wrestle control of the campaign narrative from Clinton and his other battle-tested rivals — quite a stretch.
''If we're able to do that,'' he said, ''then we will win.''
If he can't, he won't.
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EDITOR'S NOTE — Ron Fournier has covered politics for The Associated Press for nearly 20 years.