ST. PAUL, Minn. — Invigorated by back-to-back political conventions, Republican John McCain and Democrat Barack Obama grappled for the mantle of change Friday as the fall race for the presidency took off in states teeming with the independent voters they needed to win.

Within hours of accepting the Republican nomination, McCain sent an e-mail appeal for donations arguing that he and running mate Sarah Palin stood for reform in Washington. He also denounced "Democratic operatives" whom he said "have stooped lower than anyone could have imagined."

The dig appeared to be a reference to Palin's announcement earlier this week that her 17-year-old unmarried daughter was five months' pregnant. Palin, Alaska's governor, said Internet rumors about her family had led her to reveal her daughter's pregnancy. Palin has stayed out of reach of reporters and was expected to begin campaigning on her own this weekend.

Strategists for the campaigns argued Friday that McCain and Obama would be engaged in debate over new directions for public policy.

"John McCain has a record