Barack Obama easily swept Democratic presidential contests in three states yesterday, while the outsider for the Republican nomination Mike Huckabee easily won in Kansas and Louisiana.
Mr Huckabee's victories over front-runner John McCain underscored lingering conservative discontent within his party just days after the Arizona senator took an almost unassailable lead in the race to be the Republican's candidate in the presidential election in November.
Mike Huckabee tears up his federal tax form.
But Mr Huckabee's victories, fuelled by support from social and religious conservatives, were not a surprise in states with big conservative voting blocs and did little to affect Mr McCain's advantage.
Mr Huckabee told reporters after crushing McCain in Kansas: "This race is far from being over".
However, last Thursday, Mr McCain virtually clinched the nomination when his chief rival, former Mitt Romney, withdrew from the race.
Mr Huckabee is now the only major opponent for Mr McCain, who has secured more than 700 of the 1,191 delegates needed to win the Republican nomination at this summer's convention. Texan maverick Ron Paul also remains in the race.
Later tallies showed Mr McCain had narrowly beaten Mr Huckabee in Washington state, which also voted on yesterday.
Mr Huckabee captured about 60 per cent of the vote in Kansas, more than double Mr McCain's total. His victory in Louisiana was narrow.
Also in Louisiana, Democrat hopeful Mr Obama, who is locked in a bitter battle with Hillary Clinton for the Democrat nomination cruised to an easy win which he replicated in Nebraska and Washington.
He also won easily in the US territory of the Virgin Islands, which sends three delegates to the Democrat convention where final votes are declared.
Ms Clinton and Mr Obama are about even in pledged delegates but well short of the 2,025 needed to win the nomination.
There is considerable confusion, though, over how pledges should be calculated. Democratic rules allocate delegates on a proportional basis statewide and in congressional districts, meaning even the loser in each state can win large delegate votes.
It was not immediately clear how the weekend count would break down, where a combined 161 convention delegates were at stake. The Obama camp said it had won just more than 100 of the delegates.
His victories were anticipated. In Louisiana, he had been expected to benefit from a high percentage of black voters who made up about half the voters. Exit polls showed he won 80 per cent of black votes while Ms Clinton captured about 70 per cent of white votes.
The contests in Nebraska and Washington were caucuses, which require voters to turn up at specific times and typically attract more motivated people.
Mr Obama has focused on caucus states, where his advantages in organisation and grass-roots enthusiasm come into play.