Democrat Barack Obama easily beat rival Hillary Clinton in Wisconsin on Tuesday, extending his US presidential winning streak and putting pressure on Mrs Clinton to win next month in Ohio and Texas to salvage her campaign.
Republican front-runner John McCain also won in Wisconsin, taking another big step toward becoming his party's nominee in the presidential election.
Mr Obama win in Wisconsin pushed his hot streak to nine straight victories in Democratic nominating contests. Democrats in Hawaii, where Mr Obama was born and is a heavy favourite, also were voting on Tuesday.
"The change we seek is still months and miles away, and we need the good people of Texas to help get us there," Mr Obama said at a rally in Houston after noting his win in Wisconsin.
Mr McCain, an Arizona senator, beat his last remaining major rival, former Arkansas Governor Mike Huckabee, to expand his huge and essentially insurmountable lead in delegates.
"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," Mr McCain, a former Navy fighter pilot and Vietnam prisoner of war, told supporters in Columbus, Ohio.
"I will fight every moment of every day in this campaign to make sure Americans are not deceived by an eloquent but empty call for change that promises no more than a holiday from history," he said.
Mr Obama took his own shot at McCain, noting his support for President George W. Bush's economic policies and his support for a prolonged US military presence in Iraq.
"He represents the policies of yesterday and we want to be the party of tomorrow," Mr Obama said.
Mr Obama's win in Wisconsin was particularly meaningful, coming in a general election swing state with a large population of blue-collar workers - a big part of Clinton's constituency and a similar demographic to Ohio.
Mrs Clinton is the early favourite in both Texas and Ohio, although one public opinion poll in Texas on Monday showed the race in a statistical dead heat.
"We can't just have speeches. We've got to have solutions," Mrs Clinton said. "While words matter, the best words in the world aren't enough unless you match them with action."
With his Wisconsin win, Mr Obama shrugged off a weekend controversy over his uncredited use of speech lines from a friend and ally, Massachusetts Governor Deval Patrick.
"The real issue here is, if your entire candidacy is about words, they should be your own words," Mrs Clinton, a New York senator and former first lady, said in a satellite interview with a Hawaii television station.