Arizona Senator John McCain has won Republican presidential primaries in nine states, including California, while former Massachusetts governor Mitt Romney has prevailed in six, the CBC projects.

McCain's Super Tuesday victories were in California, New York, New Jersey, Connecticut, Delaware, Illinois, Missouri, Oklahoma and his home state, Arizona.

Arizona Senator John McCain and his wife, Cindy, arrive at their Super Tuesday party in Phoenix.
(Charles Dharapak/Associated Press)

Romney's came in Massachusetts, Minnesota, North Dakota, Montana, Colorado and Utah.

On the busiest primary day in American history, the biggest contest was in the most populous state, California, with 170 delegates at stake. Most of those are allotted on a district-by-district basis, which means that Romney and third-place candidate Mike Huckabee will almost certainly get some.

For McCain, his four East Coast victories alone yield a combined 184 delegates to the party's nominating convention under winner-take-all rules.

Romney's early Super Tuesday victories came on what amounted to home turf — in Massachusetts, where he was governor, and in Utah, where his fellow Mormons are concentrated.

When all of the day's results are in, 1,023 Republican delegates will have been allocated in 21 states. According to an Associated Press tally based on incomplete results, McCain won at least 420 delegates against 130 for Romney and 99 for Huckabee.

McCain went into Super Tuesday with 102 delegates, Romney 93 and Huckabee 43, AP said. It will take 1,191 delegates to win the nomination at the September convention in Minneapolis-St. Paul.

With delegate counts still under way, McCain hoped to take a commanding lead over Romney, the former front-runner, and perhaps knock him out of the race.

Former Massachusetts governor Mitt Romney waves to supporters at his Super Tuesday party in Boston.
(Bizuayehu Tesfaye/Associated Press)

"We are the Republican party front-runner for the nomination," McCain told cheering supporters in Arizona.

"We still have a long ways to go, but we are much closer to the victory we have worked so hard to achieve," he added. "I am confident we will get there."

Huckabee, a former Arkansas governor and Baptist preacher, did well in the South.

He won in Arkansas, Alabama, Georgia and Tennessee after clinching the first Super Tuesday victory, gaining all 18 delegates up for grabs in a West Virginia state convention.

On a day when Republicans, Democrats or both are voting in 24 states and American Samoa, Huckabee won the all-or-nothing vote with a second-ballot showing of 51.5 per cent.

On the first ballot, Romney got 41 per cent, Huckabee received 33 per cent and McCain 15 per cent.

"It looked like Romney was going to romp when all of a sudden in the second ballot, all of McCain's people went over to Huckabee," the CBC's Henry Champ reported from Washington.

The victory came as millions of people headed to the polls on the busiest primary day in U.S. history, a day that could make or break the Democratic and Republican candidates for the presidency.

The number of delegates won by each candidate was still being tallied.

In the Republican contest, McCain is aiming to deliver a knockout blow in the bitter battle with his closest rival, Romney.

Polls suggested McCain could secure a majority of the delegates at stake on Tuesday, or at least enough to force Romney to drop out, Champ reported.

The Republicans held votes in 21 states, while Democrats did so in 22 states and American Samoa.

McCain attacks Romney's 'terrible record'

Tempers flared between the two key Republican rivals on Tuesday as McCain attacked Romney for having a "terrible record as a governor."

Romney replied that he must be a strong contender if he's able to get under the Arizona senator's skin. 

McCain spent the first part of the day in Manhattan before heading to California, a key battleground.

"I have the judgment and the experience to lead this nation in the transcendental challenge of the 21st century, and that's the struggle against radical Islamic terrorism," McCain told a New York rally, entering to the theme from Rocky and an introduction from former rival Rudy Giuliani.

With files from the Associated Press