Barack Obama racked up two more wins on his path toward the Democratic presidential nomination, scoring victories over his rival Hillary Rodham Clinton in the Wisconsin primary and Hawaii caucuses.

Meanwhile, Arizona Senator John McCain was declared the winner in Wisconsin and Washington on Tuesday night, feeling little challenge from his main rival, former Arkansas governor Mike Huckabee. The victories have all but sewn up the nomination for McCain.

Democratic presidential hopeful Barack Obama thanked the people of Wisconsin during a rally in Houston, Texas, on Tuesday night.
(Pat Sullivan/Associated Press)

Obama's two wins mark 10 in a row for the Illinois senator and increase the pressure on Clinton to win either one or both of the crucial primaries in Ohio and Texas next March, which have 370 convention delegates up for grabs.

Wisconsin had 74 national convention delegates. There were 20 delegates at stake in Hawaii, where Obama was born and raised.

Obama's Wisconsin victory left him with 1,303 delegates in the Associated Press's count, compared with 1,233 for Clinton. It would take 2,025 to win the nomination at the party's national convention in Denver.

"The change we seek is still months and miles away," Obama said Tuesday night.

Opinion polls had suggested Clinton, a senator from New York, and Obama, a senator from Illinois, were in a dead heat for Wisconsin's 74 delegates. Voter turnout for the primary was heavy despite freezing weather.

But with the votes counted in more than 80 per cent of the state's precincts, Obama was winning 58 per cent of the vote, with 41 per cent for Clinton.

According to interviews done at polling stations, Obama appears to have won the support of about half of white female voters in Wisconsin and many of the working class voters.

The economy and trade were key issues in the race, with seven in 10 voters saying international trade has resulted in lost jobs in Wisconsin.  

Clinton made no mention of her defeat while speaking at a rally in Ohio on Tuesday night, and showed no sign of surrender. She instead noted that both she and Obama are looking to make history in the presidential race — she vying to be the first woman as U.S. president, and he aiming to be the first black U.S. president.

"Both Senator Obama and I would make history," Clinton said in Youngstown. "But only one of us is ready on Day 1 to be commander in chief, ready to manage our economy, and ready to defeat the Republicans.

"Only one of us has spent 35 years being a doer, a fighter and a champion for those who need a voice."

McCain thanks Wisconsin supporters

McCain is the strongest candidate left in the Republican race, which has seen high-profile candidates drop out, including former Massachusetts governor Mitt Romney.

"Thank you, Wisconsin, for bringing us to the point where even a superstitious naval aviator can claim with confidence and humility that I will be our party's nominee for president of the United States," McCain told supporters after watching the Wisconsin results in Ohio.

Romney, who bowed out Feb. 7, is supporting McCain and has urged his 280 delegates to do the same.

McCain needs 1,191 delegates to clinch the Republican nomination at the party convention in Minnesota next summer.

Democrats held their caucuses in Washington earlier this month, with Obama taking victory in the state.

Neither Democratic candidate travelled to Hawaii to campaign, although Clinton sent her daughter, Chelsea. The two front-runners have turned their attention to the March 4 primaries in the vote-rich states of Ohio and Texas. Clinton travelled to Ohio on Monday, while Obama left for Texas on Tuesday.

Washington state also held a Republican primary Tuesday, but results were still pending Tuesday night.

With files from the Associated Press