Know this: Change is a word you will hear over and over again during the fall campaign.

It's been a watchword for Barack Obama from the start. His strongest appeal has been his talk of generational change and new approaches to politics and public policy.

After spending much of the summer challenging Obama's credentials to lead, John McCain served notice in his acceptance speech that he too will promise change.

And there's a good reason why both candidates want to claim this one-word platform. This election is likely to decided by moderate and independent voters in swing states, and as a group they're tired of bickering, posturing and inaction. Whichever candidate wins these voters over wins the election.

McCain certainly had them in mind when he delivered these lines on Thursday:

-- "Americans want us to stop yelling at each other."

-- "I fight to restore the pride and principles of our party," he said. "We were elected to change Washington, and we let Washington change us."

-- "You know, I've been called a maverick, someone who marches to the beat of his own drum," he said. "Sometimes it's meant as a compliment and sometimes it's not. What it really means is I understand who I work for. I don't work for a party. I don't work for a special interest. I don't work for myself. I work for you."

There was humility in his speech, a trait not seen often enough in public life.

It will be a challenge (and it should be) to persuade voters that he brings change after 30 years as part of the Washington establishment and as the nominee of a party that controlled Congress for 12 of the past 14 years, the White House for going on seven years and seven of nine seats on the U.S. Supreme Court.

But McCain offered a credible case for himself. The most effective part of his speech came near the end, when he described himself as an imperfect public servant, whose commitment to public service was forged by his experience as a prisoner of war.

Much of the rest of the convention stood in sharp contrast to McCain's words, with sophomoric attacks that at times overlooked McCain's own positions (For all the talk about rights for terrorists, it was McCain who sponsored a bill that would have granted rights to prisoners at Guantanomo). So where Obama must show voters that he has ideas to match his ideals, McCain must show voters that his party shares his ideals.

Where does Sarah Palin fit in all this? My guess is her role will be working the Republican base - leading the attacks and reassuring conservatives - while McCain heads back to the middle and tries to take the mantle of change away from Obama.

The first debate is Sept. 26, three weeks from today, at the University of Mississippi. It should be a rollicking good show.

-- Jim Sweeney