Barack Obama is hoping to take a major step toward the Democratic presidential nomination when Oregon and Kentucky vote later today.
After today's vote, Obama will be able to claim a majority of pledged delegates won in the lengthy state-by-state fight with Hilary Clinton - a landmark he hopes will signal the beginning of the end of their gruelling race.
While he could still be about 50 to 75 delegates short of the 2,026 needed to win the nomination at the August convention, Obama hopes the mark will send more undecided superdelegates - party officials who can back any candidate - flooding his way.
"A clear majority of elected delegates will send an unmistakable message - the people have spoken, and they are ready for change," Obama campaign manager David Plouffe said in an e-mail message to supporters.
Clinton, who has ignored Obama's almost unassailable lead in delegates for weeks and shrugged off calls to quit the race before the last of the voting concludes on June 3, was unfazed by the approaching milestone.
"There is no way that this is going to end any time soon because we're going to keep fighting for the nomination," she told a rally in Prestonsburg, Kentucky, one of five events on a long last day of campaigning in the state.
She said superdelegates should reconsider the race because she would be a stronger foe for Republican John McCain in November's presidential election. Her victories in big states like Pennsylvania and Ohio gave her a broader base of support than Obama, she said.
"There has been a lot of analysis about which of us is stronger to win against Senator McCain, and I believe I am the stronger candidate," the New York senator said, pointing to an evaluation by President George W. Bush's former chief political strategist, Karl Rove, to back up her case.
Obama is favoured to win in Oregon, where opinion polls give him a lead hovering between 4 per centage points and double-digits, and Clinton is a big favourite in Kentucky. The two states have a combined 103 delegates at stake.
All voting ends in Kentucky at 7 p.m. EDT (12 a.m. Irish time) and Oregon's mail balloting will end at 8 p.m. PDT/11 p.m. EDT (4 a.m. Irish time). Results are expected shortly after.
Obama contends the remaining undecided superdelegates, who have been trending his way heavily in recent weeks, should support him since he won the most delegates in state voting.
The Illinois senator will celebrate today's returns at a rally in Iowa, a general election battleground where he made his breakthrough with a big win in the first Democratic contest on January 3.
A delegate count by MSNBC gives Obama 1,901 delegates to Clinton's 1,724. He picked up five more superdelegates on Monday, including Sen. Robert Byrd of West Virginia.
After today's vote, just three more contests will remain with 86 delegates at stake. Slightly more than 200 superdelegates remain uncommitted.
Obama has been cautious about pushing Clinton too hard to leave the race. Both candidates have avoided criticizing each other since Obama's recent win in North Carolina moved him closer to claiming the nomination.
Obama has focused in recent weeks on the general election fight with McCain.
The Clinton campaign sent a memo to reporters saying any Obama effort to declare himself the nominee on Tuesday would be "a slap in the face" to Clinton supporters.
"Premature victory laps and false declarations of victory are unwarranted. Declaring 'mission accomplished' does not make it so," Clinton spokesman Howard Wolfson said.