In their hard-fought duel for the Democratic nomination, Obama won 11 states and Clinton took nine but that included the two biggest prizes of the night -- California and New York -- on the biggest day of U.S. presidential voting ahead of November's election.
"There is one thing on this February night that we do not need the final results to know: Our time has come," Obama told cheering supporters in Chicago. "Our movement is real, and change is coming to America.".
McCain had had hoped to nail down the nomination with a big night and his nine wins included California and several big Northeastern states, but rival Mitt Romney took six states and Mike Huckabee won five.
"Tonight, I think we must get used to the idea that we are the Republican Party frontrunner for the nomination," McCain said in Scottsdale, Arizona. "And I don't really mind it one bit.".
The biggest prize of the night was California, which offers the country's biggest haul of delegates to party conventions that choose the parties' presidential candidates for the Nov. 4 election to succeed President George W. Bush. U.S. media had predicted Clinton and McCain would win.
The mixed outcome in the coast-to-coast voting, with all contenders in both parties scoring at least five wins, appeared certain to prolong the hard-fought nominating races in both parties. More contests in a half-dozen states are slated in the coming week.
The Clinton and Obama camps said they expected the count of delegates for the night to be relatively even. "This is not going to be decided tonight," Democratic Party Chairman Howard Dean said on MSNBC.
National exit polls showed more than half of Democratic voters ranked the ability to bring change as the top attribute for a candidate. Nearly one-quarter of Democrats voting in the party's 22 contests ranked experience, Clinton's selling card, as the most important attribute.
About 44 percent of Republican voters preferred a candidate who shared their values, while one-quarter wanted a candidate with experience.
More than half the total delegates to the Democratic convention in August and about 40 percent of the delegates to the Republican convention in September will be apportioned in Tuesday's voting.
Economic worries -- plunging housing values, rising energy and food prices, jittery financial markets and new data showing a big contraction in the service sector -- eclipsed the Iraq war as voters' top concern in both parties, exit polls showed.