PORTLAND, Ore. -- Only days after 70,000 people gathered on Portland's waterfront to roar their approval for Democratic presidential hopeful Barack Obama, the state's voters on Tuesday handed him a resounding victory over Hillary Rodham Clinton in the state's primary election.

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It was the most exciting primary this progressive-leaning state has seen in 40 years, and one that drew record participation among Oregon's Democratic voters. A total of 52 convention delegates were at stake in the Oregon primary.

Check: Election results

With half of the expected vote counted Tuesday night, Obama was winning with 57.6 percent of the vote to Clinton's 42.3 percent.

At a raucous Obama victory celebration Tuesday night, Oregon Congressman Earl Blumenauer noted that Clinton and former President Bill Clinton and daughter Chelsea "had practically lived in Oregon for the past month," making dozens of campaign stops.

"This was nothing negative about the Clintons," Blumenauer said of Obama's huge Oregon victory. "It was just people reacting to Barack Obama. People are ready for change, and they understand that Barack Obama is ready to go. He is the guy who can do it, and people in Oregon are ready to help."

Former Gov. Barbara Roberts, another key Obama supporter, summed up her feelings by exclaiming, "How sweet it is!"

"I don't remember a race like this one. It was so clear that this was a remarkable candidate at exactly the right time in American history," Roberts said.

The mood at Hillary Clinton's headquarters was subdued Tuesday, with supporters seeming unsurprised by the results, which had been widely predicted by pollsters.

Josh Kardon, chairman of Clinton's Oregon campaign, said he didn't think the protracted battle between Obama and Clinton would hamper the Democrats' chances of defeating Sen. John McCain in November.

"The Democratic Party race won't be hurt by too much democracy. Let's let the people decide and we'll be fine in the fall," Kardon said.

Both of the contenders had crisscrossed the state in recent weeks, but polling just before the election showed Barack winning across most demographic categories.

An exit poll showed women were evenly divided between Clinton and Obama, but men supported Obama 2-to-1, dooming Clinton's bid in Oregon even without the strong support Obama received in other categories.

The Illinois senator was heavily favored across nearly all age, income and education categories.

Clinton, by comparison, found support only among those older than 65, the working poor and voters who never attended college.

The Clinton voters reflected her strong showing among blue-collar voters with a high school education in other parts of the nation, but her advantage quickly disappeared as income and education increased.

Younger voters strongly backed Obama, and he was heavily favored by all voters making more than $30,000 and those who had at least attended college.

Voters who described themselves as "very liberal" voted 2-to-1 for Obama, and he was favored by those who said they were "somewhat liberal" and "moderate."

The youngest age group, voters 18 to 24, voted 3-to-1 for Obama while those who said it was their first time voting in a primary supported him 2-to-1, both in keeping with the state's liberal and progressive image.

Obama also did very well in large cities where liberal voters typically hold sway, while support was about evenly divided between him and Clinton in more conservative rural areas.

The exit poll by Edison Media Research and Mitofsky International was conducted by telephone May 12-18 among 1,201 people who said they definitely had voted or definitely would vote in Oregon's vote-by-mail Democratic primary. The margin of error was plus or minus 3 percentage points.

Oregonians have been drawn to this year's primary knowing that for the first time in four decades, their votes are critical in determining the Democratic nominee.

That and excitement over Obama resulted in a turnout expected to reach as much as 60 percent, the highest voter participation in an Oregon primary since the 1968 Democratic race between Robert F. Kennedy and Eugene McCarthy.

From early in the campaign, Oregon was considered Obama territory.

Obama visited Oregon four times. The first was a September rally in Portland that drew 3,400 people and a fundraiser that netted $200,000.

The last ended with a riverfront rally in Portland on Sunday that drew 75,000 people -- Obama's largest campaign rally. "Wow. Wow. Wow," he told the legions of supporters. "This is spectacular."

That big rally wasn't the first time Obama made a splash in Portland.

On a visit in March, New Mexico Gov. Bill Richardson, once an ally of the Clintons, endorsed Obama as "a once-in-a-lifetime leader." That was at a rally that drew 12,000. Later that day, Obama drew 9,000 at the University of Oregon.

By contrast, Clinton's three visits produced crowds that generally numbered in the hundreds, and last week she canceled planned stops and stayed in Kentucky.

Much of her Oregon work was done by Bill and Chelsea Clinton, who insisted that the national race was not over. Between them, they logged six trips to the state that included 47 events or stops.