US Democratic front-runner Mr John Kerry has held off a strong challenge from main rival Mr John Edwards to win the Wisconsin primary in his bid to secure the party's presidential nominatioon.
However, the narrowness of the winning margin dented Mr Kerry's runaway momentum and pumped new life into the party's presidential race.
Senator John Kerry
The surprising showing by Mr Edwards extended the race to find a challenger for President George W. Bush for at least two more weeks, until a potentially decisive March 2nd "Super Tuesday" round of 10 contests in big states like New York, Ohio and California.
Former front-runner Mr Howard Dean stumbled to a distant third-place finish that effectively ended his campaign. He headed home to Vermont to ponder his future before announcing a decision on whether to pull the plug.
Mr Kerry, who has dominated the race with wins in 15 of the first 17 contests, heads into "Super Tuesday" with a clear shot at wrapping up the nomination but will have to contend with a one-on-one matchup with a revitalized Mr Edwards.
With about 95 per cent of the vote counted, Mr Kerry led Mr Edwards by 40 per cent to 35 percent, with Mr Dean trailing at 18 per cent.
Mr Kerry and his advisers played down the showing by his main rival. "A win is a win," the Senator said before the final results.
Mr Kerry, whose campaign was given up for dead six weeks ago, already has the support of more than one-quarter of the 2,162 delegates needed to win the nomination in July and has more delegates than his remaining rivals combined.