At the heart of Obama's speech in Iowa tonight is one simple word that may ultimately be his most potent weapon against McCain:

I will leave it up to Senator McCain to explain to the American people whether his policies and positions represent long-held convictions or Washington calculations, but the one thing they don’t represent is change.
 
Change is a tax code that rewards work instead of wealth by cutting taxes for middle-class families, and senior citizens, and struggling homeowners; a tax code that rewards businesses that create good jobs here in America instead of the corporations that ship them overseas.  That’s what change is.
 
Change is a health care plan that guarantees insurance to every American who wants; that brings down premiums for every family who needs it; that stops insurance companies from discriminating and denying coverage to those who need it most.
 
Change is an energy policy that doesn’t rely on buddying up to the Saudi Royal Family and then begging them for oil – an energy policy that puts a price on pollution and makes the oil companies invest their record profits in clean, renewable sources of energy that will create five million new jobs and leave our children a safer planet.  That’s what change is.
 
Change is giving every child a world-class education by recruiting an army of new teachers with better pay and more support; by promising four years of tuition to any American willing to serve their community and their country; by realizing that the best education starts with parents who turn off the TV, and take away the video games, and read to our children once in awhile.
 
Change is ending a war that we never should’ve started and finishing a war against Al Qaeda in Afghanistan that we never should’ve ignored.  Change is facing the threats of the twenty-first century not with bluster, or fear-mongering, or tough talk, but with tough diplomacy, and strong alliances, and confidence in the ideals that have made this nation the last, best hope of Earth.  That is the legacy of Roosevelt, and Truman, and Kennedy.
 
That is what change is.
 
That is the choice in this election. 

Whatever you think of the merits of the candidates, Obama clearly has the far stronger claim to "change." And when 85 percent of Americans are unsatisfied with the direction of the country, that's an awfully powerful advantage. 

P.S. Obama even referred to "more of the same versus change"--which is a very interesting historical echo

--Michael Crowley