Mr McCain won the big states of California and New York, although Mike Huckabee did better than expected.
For the Democrats, Hillary Clinton won in New York and California, but rival Barack Obama also did well by winning in 13 states.
It was the biggest day in the race to pick candidates in November's election.
But the campaigns are already looking ahead to contests on Saturday in Louisiana, Nebraska and Washington state and 12 February primaries in Maryland, Virginia and Washington DC.
Race not yet run
Mr McCain's gains seriously wounded his main rival, Mitt Romney, the BBC's James Coomerasamy in Washington says.
Mr McCain also won in Illinois, Oklahoma, New Jersey, Missouri, Connecticut, Delaware, and his home state of Arizona.
In many Republican races, the winner takes all the state delegates to the national party convention. New York alone comes with 87 delegates.
The Democratic race was as tight as forecast, although Mrs Clinton secured the two biggest prizes.
In New York, her home state, she captured about 57% of votes to Mr Obama's 40%.
In California, with most precincts counted, Mrs Clinton had won 52% of Democratic votes and Mr Obama about 42%.
Mrs Clinton also took Arizona, Massachusetts and New Jersey, as well as the southern, rural states of Oklahoma, Tennessee and Arkansas.
However Mr Obama won a greater number of states, namely Alabama, Alaska, Colorado, Connecticut, Delaware, Georgia, Idaho, Kansas, Minnesota, Missouri, North Dakota, Utah and his home state of Illinois.
| | I think we must get used to the idea that we are the Republican Party front-runner John McCain |
The Democratic caucuses in New Mexico remained unsettled. Mrs Clinton had a 117-vote lead when the party shut down its counting operation until 1600 GMT on Wednesday.
Before the final results were in, Mr Obama told supporters: "We don't need the final results to know our time has come."
In terms of delegates captured, Mrs Clinton was only marginally ahead - under the Democrats' system of proportional distribution.
Both are still well short of the 2,025 needed to secure the party's nomination.
'All the way'
Overall, voters were choosing 42% of delegates on Super Tuesday.
| | REPORTS FROM THE CAMPS |
In each state's primary or caucus, successful candidates are awarded delegates who formally choose the party's nominee at the national convention in six months' time.
In Arizona, Mr McCain's told supporters: "We must get used to the idea that we are the Republican Party front-runner for the presidency of the United States."
However it was Mr Huckabee who took the first state to announce a result, West Virginia.
| | WHAT IS SUPER TUESDAY? 24 states holding simultaneous contests to help decide the Democratic and Republican presidential nominations About 40% of each party's delegates - who will choose the candidate - are up for grabs Key states electing large numbers of delegates include California, New York and Illinois |
Overall, he went on to confound the polls, which had put him in a distant third, and came not far behind Mr Romney.
He won across the south, in Arkansas, where he used to be governor, as well as Alabama, Georgia and Tennessee.
"We are still on our feet and much to the amazement of many we are getting there folks," he told supporters in Arkansas.
Mr Romney won in Colorado, North Dakota, Massachusetts, Minnesota, Montana, Alaska and Utah.
The former Massachusetts governor said he was not about to drop out of the race and was "going all the way to the White House".
http://news.bbc.co.uk/go/pr/fr/-/2/hi/americas/7229895.stm

