Barack Obama is projected to take a primary vote in Wisconsin, a blow to his rival for the Democratic nomination to run for president, Hillary Clinton.
Barack Obama has extended his lead over his rival, Hillary Clinton, in the contest to win the Democratic nomination to run for US president.
John McCain is projected to win for the Republicans, boosting his front-runner status in his party's contest.
With most of the votes counted, Mr Obama, the senator for Illinois, has won the primary in Wisconsin - his ninth victory in a row.
Mr McCain appeared to target Mr Obama in his victory speech as he promised to ensure Americans were "not deceived by an eloquent but empty call for change".
John McCain has won for the Republicans, boosting his front-runner status in his party's contest.
Mr McCain is also projected to win a Republican primary in Washington state.
Mr McCain is projected to win a Republican primary in Washington state.
Meanwhile, Mr Obama is expected to win a Democratic caucus in Hawaii, where the Illinois senator was born and 20 delegates are at stake.
Meanwhile, Mr Obama is expected to win a Democratic caucus in Hawaii, where the Illinois senator was born and 20 delegates are at stake.
Caucusing does not begin until 1900 local time on Tuesday (0500 GMT Wednesday).
Caucusing was due to begin at 1900 local time on Tuesday (0500 GMT Wednesday).
Seeking momentum
Seeking momentum
The BBC's Jonathan Beale says Wisconsin was a significant victory for Barack Obama, marking his ninth win in a row since the votes on so-called Super Tuesday, 5 February.
The BBC's Jonathan Beale says Wisconsin was a significant victory for Mr Obama, eating into Mrs Clinton's support base.
With 95% of the ballots counted, Mr Obama had 58% of the vote to Mrs Clinton's 41%.
Democrats
Hillary Clinton13 states, 1,218 delegates
Arizona, Arkansas, California, Florida, Massachusetts, Michigan, Nevada, New Hampshire, New Jersey, New Mexico, New York, Oklahoma, Tennessee
Barack Obama21 states, 1,281 delegates
Alabama, Alaska, Colorado, Connecticut, Delaware, Georgia, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Maryland, Minnesota, Missouri, Nebraska, North Dakota, South Carolina, Utah, Virginia, Washington state2,025 delegates needed for nomination. Source AP (includes all kinds of delegates)Q&A: US election delegates
Republicans
Mike Huckabee8 states, 245 delegates
Alabama, Arkansas, Georgia, Iowa, Tennessee, West Virginia, Kansas, Louisiana
John McCain15 states, 903 delegates
Arizona, California, Connecticut, Delaware, Florida, Illinois, Maryland, Missouri, New Hampshire, New Jersey, New York, Oklahoma, South Carolina, Virginia, Washington state
Mitt Romney11 states, 253 delegates
Campaign suspendedAlaska, Colorado, Maine, Massachusetts, Michigan, Minnesota, Montana, Nevada, North Dakota, Wyoming, Utah1,191 delegates needed for nomination. Source: AP (includes all kinds of delegates)
Democrats
Hillary Clinton13 states, 1,218 delegates
Arizona, Arkansas, California, Florida, Massachusetts, Michigan, Nevada, New Hampshire, New Jersey, New Mexico, New York, Oklahoma, Tennessee
Barack Obama21 states, 1,281 delegates
Alabama, Alaska, Colorado, Connecticut, Delaware, Georgia, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Maryland, Minnesota, Missouri, Nebraska, North Dakota, South Carolina, Utah, Virginia, Washington state2,025 delegates needed for nomination. Source AP (includes all kinds of delegates)Q&A: US election delegates
Republicans
Mike Huckabee8 states, 245 delegates
Alabama, Arkansas, Georgia, Iowa, Tennessee, West Virginia, Kansas, Louisiana
John McCain15 states, 903 delegates
Arizona, California, Connecticut, Delaware, Florida, Illinois, Maryland, Missouri, New Hampshire, New Jersey, New York, Oklahoma, South Carolina, Virginia, Washington state
Mitt Romney11 states, 253 delegates
Campaign suspendedAlaska, Colorado, Maine, Massachusetts, Michigan, Minnesota, Montana, Nevada, North Dakota, Wyoming, Utah1,191 delegates needed for nomination. Source: AP (includes all kinds of delegates)
It is not just about momentum, our correspondent says, but about Mr Obama eating into Mrs Clinton's support base.
It is a major disappointment for Mrs Clinton, the senator for New York, who had been hoping to restore momentum to her campaign.
Wisconsin is a largely white, working class state - the kind of place where Mrs Clinton has done well in the past, he adds.
Instead, Mr Obama was reported to have gained almost equal support from white women, and to have polled well from working-class Democrats - both groups which have usually supported Mrs Clinton.
Early exit polls suggested Mr Obama tied with Mrs Clinton for votes among women overall and substantially eroded her lead among white women, previously a core base for her. She continued to do well among older voters, however.
Mr Obama also took the youth vote and six out of 10 self-described independent voters, according to exit polls for ABC.
Mr Obama also picked up the support of six out of 10 self-described independent voters, according to exit polls for Associated Press.
But he and Mrs Clinton are already looking ahead to March's bigger contests in Ohio and Texas, seen by analysts as crucial to her credibility as a candidate.
With 83% of the ballots counted, Mr Obama had 58% of the vote to Mrs Clinton's 41%.
Speaking at a victory rally in Houston, Texas, Mr Obama said: "The change we seek is still months and miles away and we need to get all of Texas to help us get there."
Speaking at a victory rally in Houston, Texas, Mr Obama said: "The change we seek is still months and miles away and we need to get all of Texas to help us get there."
He also sought to counter criticism that his campaign is about rhetoric rather than action.
In pictures: Wisconsin votes It was "going to take more than big rallies, it is going to require more than rousing speeches" and policy papers to win, he said.
"It is going to require something more, because the problem that we face in America today is not a lack of good ideas, it's that Washington has become a place where good ideas go to die."
He and Mrs Clinton have been looking ahead to March's bigger contests in Ohio and Texas, seen by analysts as crucial to her credibility as a candidate.
Some have suggested the vote in Wisconsin could be an indicator as to how she may fare in such similarly industrial, blue-collar states as Ohio, and Pennsylvania in April.
Addressing a rally in Youngstown, Ohio, Mrs Clinton said the primary campaign was "about picking a president who relies not just on words but on work - hard work to get America back to work".
Addressing a rally in Youngstown, Ohio, Mrs Clinton said the primary campaign was "about picking a president who relies not just on words but on work - hard work to get America back to work".
Before the results from Wisconsin were calculated, Mr Obama held a slight lead over Mrs Clinton, with 1,280 delegates to her 1,218.
Before the results from Wisconsin were calculated, Mr Obama held a slight lead over Mrs Clinton, with 1,280 delegates to her 1,218.
It will take 2,025 delegates to secure the Democratic nomination at the party's national convention this summer.
It will take 2,025 delegates to secure the Democratic nomination at the party's national convention this summer.
McCain favourite
McCain favourite
Mr McCain, the senator for Arizona, appeared to target Mr Obama in his victory speech as he promised to ensure Americans were "not deceived by an eloquent but empty call for change".
On the Republican side, the race between Mr McCain and Mike Huckabee, a former Arkansas governor, continues.
On the Republican side, the race between Mr McCain and Mike Huckabee, a former Arkansas governor, continues.
Mr McCain's win in Wisconsin will be a boost to his front-runner status
But Mr McCain now has almost four times as many delegates as Mr Huckabee and the support of the party establishment.
Mr McCain now has almost four times as many delegates as his main rival, Mike Huckabee.
With 83% of the vote counted in Wisconsin, he led by 55% of the vote compared to 37% for Mr Huckabee and 5% for Texas Congressman Ron Paul.
With 95% of the vote counted in Wisconsin, he led with 58% of the vote compared to 37% for Mr Huckabee and 5% for Texas Congressman Ron Paul.
Giving a victory speech in Columbus, Ohio, Mr McCain said: "Thank you, Wisconsin, for bringing us to the point where even a superstitious naval aviator can claim with providence and humility that I will be our party's nominee for president."
Throwing forward to the general election contest in November, when the chosen Republican and Democratic contenders will go head to head, he seemed to suggest that Mr Obama might lack the necessary experience to lead.
"Will we heed appeals for change that ignore the lessons of history and lack confidence in the intelligence and ideals of free people?" he asked.
"I will fight every moment of every day in the campaign to make sure Americans are not deceived by an eloquent but empty call for change."
Conservatives elusive
Early exit polls for AP suggested Mr McCain had made headway with some core Republican voters, beating Mr Huckabee overwhelmingly for the support of moderate Republicans.
Early exit polls for AP suggested Mr McCain had made headway with some core Republican voters, beating Mr Huckabee overwhelmingly for the support of moderate Republicans.
Mike Huckabee can still count on a chunk of the conservative vote
The Washington Republican primary is the second vote in a two-part nominating contest - half their delegates were decided earlier in a caucus on 9 February, which was narrowly won by Mr McCain.
However, he still lost to Mr Huckabee among the quarter of those Republican voters describing themselves as "very conservative" and among evangelical Christians.
With 53% of Tuesday's vote counted, Mr McCain had amassed 48% to Mr Huckabee's 21% and Mr Paul's 7%.
On Monday, former President George Bush Senior endorsed Mr McCain in his bid to be the Republicans' presidential nominee and dismissed criticism of his record as "grossly unfair".
The Washington Republican primary was the second half of a two-part nominating contest. The state's Republicans held a caucus on 9 February, which was narrowly won by Mr McCain.
With 38% of Tuesday's vote counted, Mr McCain had amassed 48% to Mr Huckabee's 21%.
Republicans will only allocate about half their delegates on the basis of the primary - the rest were decided earlier in the caucus.
Washington state's Democrats are also holding a primary but their delegates to the party's summer nominating convention have already been chosen on the basis of caucuses.
Washington state's Democrats are also holding a primary but their delegates to the party's summer nominating convention have already been chosen on the basis of caucuses.
