LOUISVILLE, Ky. (AP) -- A top Barack Obama adviser urged Democrats to unite behind the Illinois senator for the fall campaign and bring the marathon contest for the presidential nomination to a close, but some Hillary Rodham Clinton supporters weren't buying that as Oregon and Kentucky held primaries Tuesday.

In a full page ad in The New York Times, Clinton's female supporters demanded that she stay in the race despite overwhelming odds.

"We want Hillary to stay in this race until every vote is cast, every vote is counted, and we know that our voices are heard," said the ad, paid for by the WomenCount political action committee.

But former Sen. Tom Daschle, a key Obama adviser, said now is the time for Democrats to coalesce behind Obama in order to defeat Republican nominee-in-waiting John McCain.

"We want to begin the process of bringing this party together, and I think that over the last few weeks we've seen indications at virtually all levels in both campaigns that there's a desire to do that," Daschle told CBS' "The Early Show." "That doesn't mean we're going to do it tomorrow or the next day, but clearly there is a desire to unify."

Only three primaries remain after Tuesday - Puerto Rico on June 1 and South Dakota and Montana on June 3.

Obama was favored in Oregon, where supporters delivered the largest crowd of his campaign on Sunday.

Clinton vowed there was "no way that this is going to end anytime soon" as she campaigned Monday across Kentucky, a state she was expected to win.

Polls opened in Kentucky at 6 a.m. EDT and elections officials reported few problems.

Scott Mendel, a 54-year-old firefighter who voted at a Methodist church in Louisville, Ky., said it was a hard decision between the two Democratic candidates, but he chose Obama.

"It's more about who you can trust and who can do a good job," Mendel said.

Tony Clark, 61, a real estate agent in Owensboro in western Kentucky, said the issue that determined his vote for Clinton was health care.

"We're at a point in America that the one thing that is crippling us is not gasoline, it is health care," Clark said. "What we want is the same thing the United States senators have got. We want their program as a citizen or we want to take away their program."

Obama is reaching for a symbolic tipping point in Oregon and Kentucky. Regardless of who prevails in those states, Obama is on track to secure the largest share of delegates who could be won in the long slog of primaries and caucuses since the snows of January.

If there were to be practical dividends in that achievement, they would come from persuading the remaining uncommitted superdelegates - the party insiders who are not tied to primary or caucus results - to pick up the pace of their endorsements.

Enough of them have done so already to transform Clinton's hopes for the nomination from improbable in recent weeks to worse.

Still, the New York senator soldiered on through event after event, ending her night Monday in Louisville before a crowd of several hundred, her voice raspy from the stage.

"There are a lot of people who wanted to end this election before you had a chance to vote," she said, husband and former President Clinton at her side. "I'm ready to go to bat for you if you'll come out and vote for me."

She argued at one stop that she is the "more progressive candidate" and dismissed Obama's large crowds, like the record rally by an estimated 75,000 in Portland on Sunday.

Clinton said Obama, who has refused to debate her since before the Pennsylvania primary last month, would "rather just talk to giant crowds than have questions asked."

Obama planned to spend the latest primary day in Iowa, the state of his opening electoral success.

He rarely mentions Clinton now, except to praise her "magnificent" campaign - praise he can now afford to give his rival. He is tangling almost solely with McCain in a prelude to the fall general campaign.

A look at some of the numbers at play going into Tuesday's contests:

-Obama was 17 delegates short of reaching a majority of the 3,253 pledged delegates available in all state contests.

-Oregon offered 52 delegates; Kentucky had 51.

-Counting aligned superdelegates as well, Obama had a total of 1,916 and Clinton had 1,721, according to the latest Associated Press count. That placed Obama just more than 100 delegates short of the 2,026 needed to clinch the nomination.

Democratic Party officials are scheduled to meet last this month to decide whether and how to count delegates from Florida and Michigan primaries that were held in defiance of the party's rules.

Clinton won both, but Obama kept his name off the ballot in Michigan and neither candidate campaigned in either state. Counting those delegates in some way could tighten the race but not, absent other surprises, tip the contest to Clinton.

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Calvin Woodward reported from Washington. Associated Press Writer Brett Barrouquere in Louisville, Ky., contributed to this report.

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