( dpa )- African-American candidate Barack Obama beat former first lady Hillary Clinton in two state contests Saturday for the Democratic presidential nomination, further tightening the party's race.
Obama held 2-1 margins over Clinton after party caucuses in Nebraska and in the north-western state of Washington, the biggest prize on a night of Democratic voting in three states from the Gulf of Mexico to the Pacific Coast.
Exit polls also showed Obama, 46, ahead in Louisiana after Saturday's Democratic primary, but it was too early to call a winner in the Gulf Coast state. McCain and Huckabee were neck-and-neck in early results there.
On the Republican side, former Arkansas governor Mike Huckabee - the only possible obstacle to Senator John McCain's presidential nomination - easily won caucuses in the Midwestern state of Kansas.
Obama, 46, could overtake Clinton, 60, in the state-by-state Democratic delegate count on the strength of his latest showing. He had already won 15 states heading into Saturday compared to Clinton's 12.
After Saturday's votes, the nomination battles move on with Democratic caucuses Sunday in Maine and on Tuesday with voting by both parties in jurisdictions clustered along the Potomac River - Virginia, Maryland and the federal city of Washington.
At a rally Saturday night the Virginia capital of Richmond, Clinton described the problems of war, economic uncertainty and social inequality facing the next president, who takes office on January 20, 2009.
"Our task tonight is to make sure that president is a Democrat," she said.
Obama, seeking to become the first black US president, has consistently done well in states where Democrats hold caucuses - local party meetings that reward fervour by requiring voters to assemble for an hour or more to voice their preferences for a presidential candidate.
"There's no doubt that ( Clinton) hasn't generated the kind of grass-roots enthusiasm that we have," Obama was reported as telling journalists on his campaign plane.
Huckabee leapt from obscurity with a surprise win last month in Iowa, the first state on the calendar of 2008 intra-party contests to decide the major-party presidential nominations.
With little money and a small campaign organization, he was unable to capitalize on his Iowa breakout until so-called Super Tuesday earlier this week, when he won five Southern states.
A Baptist minister before entering politics, Huckabee has appealed largely to conservative Christians and other voters on the right wing of the centre-right Republican Party.
Kansas has a strong evangelical movement, and with the caucus results completed statewide, Huckabee had 60 per cent to McCain's 24 per cent.
McCain, who holds a towering lead over Huckabee in delegates to the Republican presidential convention in September, is still the overwhelming frontrunner for the party's nomination, after his closest rivals dropped out in recent weeks.