WASHINGTON: Barack Obama has swept four contests in his historic and deadlocked battle with Hillary Rodham Clinton, slicing into her slim delegate lead and completing his best night of the Democratic presidential campaign.

Obama won the Louisiana primary and the Nebraska and Washington state caucuses and notched a victory in the US Virgin Islands, too. The first-term senator's winning margins were substantial, ranging from two-thirds of the vote in Washington and Nebraska to nearly 90 percent in the Virgin Islands.

On the Republican front, Mike Huckabee snatched two victories on Saturday from presumptive Republican candidate John McCain. Although his wins in Kansas and Louisiana are no threat to McCain's frontrunner status, it reflects the difficulty the latter faces in wooing the party's core conservative bloc. McCain won the night's third Republican race, in Washington state.