Obama rides momentum before 'Potomac Primaries'

WASHINGTON - Democrat Barack Obama is riding a burst of momentum into Tuesday's U.S. presidential nominating contests with a string of weekend wins, while Republican John McCain received praise from onetime rival President George W. Bush as he tries to woo conservatives.

Locked in a deadlocked state-by-state battle with Obama for the Democratic nomination, Sen. Hillary Clinton replaced her campaign manager after Saturday's losses to the Illinois senator.

Obama, who would be the first black president, scored a win in Maine on Sunday after sweeping caucuses in Louisiana, Nebraska and Washington a day earlier.

"We have now won on the Atlantic coast, we've won on the North Coast, we've won on the Pacific Coast, and we've won in between those coasts," Obama said at a rally in Virginia Beach, Virginia after the Maine results were announced.

The Clinton staff shake-up came before the "Potomac Primary" on Tuesday when both parties hold contests in the U.S. capital and in neighbouring Maryland and Virginia.

At a rally at a university in Bowie, Maryland, Clinton told the audience their choice "matters this year more than ever" and they should "pick a Democratic nominee who has been tested and vetted and can go the distance against John McCain."

Clinton, a New York senator who would be the first woman president, did not mention Obama's Maine victory nor did she discuss the staff shake-up.

Clinton named Maggie Williams, a top aide when she was first lady, to take over as campaign manager from Patti Solis Doyle, who was moved into the role of senior adviser.

Larry Sabato, a political science professor at the University of Virginia, said the shuffle indicated Clinton and her aides are concerned about the direction of her campaign.

"If you're the ocean liner of the Hillary Clinton campaign and you're trying to change course, this is how you would do it," he said. "All of the pieces are changing."

While Clinton may be in a bit of trouble, "It's not over," Sabato said, adding that if she does well in Ohio, Texas and Pennsylvania, she could win the nomination.

Clinton and Obama have been about even in pledged delegates but well short of the 2,025 needed to win the Democratic nomination for November's presidential election.

Obama was leading in opinion polls and was expected to do well in Tuesday's balloting. Both Democrats and McCain, an Arizona senator, planned appearances across the region on Monday.

McCain took a short break from campaigning but received a vote of confidence as well as some advice from Bush as he tried to ease fears among conservative Republicans that McCain was too liberal.

"If John's the nominee, he has got some convincing to do to convince people that he is a solid conservative," Bush said on Fox News Sunday. "And I'll be glad to help him if he's the nominee, because he is a conservative."

Bush and McCain have been bitter rivals in past election battles and have had many disagreements over issues like prisoner interrogation and taxes.

McCain became the likely Republican nominee last week with the withdrawal of his chief rival, former Massachusetts Gov. Mitt Romney. Conservative Republicans are unhappy with the prospect of McCain as the nominee because of his voting record on such issues as taxes, immigration, stem cell research and campaign law reform.

Former Arkansas Gov. Mike Huckabee remains in the Republican race. He beat McCain in Louisiana and Kansas on Saturday and ran a very close second in Washington state.

Rep. Ron Paul of Texas, far behind in the Republican race, was a close third in Washington.