WASHINGTON (Reuters) - Supporters of Barack Obama backed away on Sunday from calls for Hillary Clinton to drop out of the presidential race as Democrats faced a long summer of bitter fighting to win the party’s White House nomination.

Democratic presidential candidates Senator Hillary Clinton (L) (D-NY) and Senator Barack Obama (D-IL) square off in the last debate before the Ohio primary in Cleveland, Ohio February 26, 2008. Supporters of Obama backed away on Sunday from calls for Clinton to drop out of the presidential race as Democrats faced a long summer of bitter fighting to win the party's White House nomination. REUTERS/Aaron Josefczyk

In an interview published in The Washington Post, Clinton said she would fight all the way to the late August nominating convention, where a candidate will be chosen to face presumptive Republican nominee John McCain in the November election.

“I think the race should continue,” said New Mexico Gov. Bill Richardson, a former Democratic presidential candidate who supports Obama. “She has every right to stay in the race. She’s run a very good campaign.”

Some Obama backers have called on New York Sen. Clinton to give up, citing the Illinois senator’s leads in the popular vote, states won and delegates to the convention to choose the nominee.

But Clinton has used those calls to rally her supporters, saying Washington insiders are trying to force her out before all Democrats have voted. She also stressed the need for new votes in Florida and Michigan, whose earlier primary votes were rejected because they violated party rules.

“I have no intention of stopping until we finish what we started and until we see what happens in the next 10 contests and until we resolve Florida and Michigan,” Clinton said in the Post interview. “And if we don’t resolve it, we’ll resolve it at the convention.”

CAMPUS RALLY

With the next big contest coming in Pennsylvania on April 22, Clinton and McCain took much of the day off, but Obama campaigned at Pennsylvania State University. Some 22,000 people came to listen to him speak at an open air rally, which aides said was one of the biggest events of the Democratic campaign.

“I believe that the Democrats will be unified as soon as this nomination is settled. We will be unified because we understand that we do not want to be clinging to the policies of the past. We are the party of the future,” Obama said.

College students have been some of Obama’s most active supporters and in Pennsylvania he must score big among them if he is to do well against Clinton.

“You will have a president who has taught the constitution and believes in the constitution and will obey the constitution of the United States of America,” Obama told the crowd, making a comparison between himself and President George W. Bush.

Obama supporters hit the Sunday morning television talk shows to play down talk that Clinton should quit -- at least before the final nomination contests on June 3.

But after that, with neither Democratic contender likely to have captured the 2,024 delegates needed to face McCain, they wanted a quick resolution so the fight does not last all summer. The outcome will probably lie with several hundred “superdelegates” -- party leaders and elected officials free to vote for either candidate.

Slideshow ( 4 images )

“After June 3, it’s important that Democrats come together and not be so divided as we have been,” Richardson said on CBS’ “Face the Nation.” “But I think it’s important that, at the end of the June 3 date, we look at who has the most delegates, who has the most popular vote, who has the most states.”

That would most likely favor Obama. But Clinton backers did not see the need to hurry.

“Neither Sen. Clinton nor Sen. Obama, based on what people say the math is, can get the required number of delegates. And so you have to play it out until the end,” Philadelphia Mayor Michael Nutter, a Clinton backer, said on the CBS show.

Tennessee’s Democratic Gov. Phil Bredesen has proposed the superdelegates get together to make their choices after June 3 so the party can heal its wounds and go after the Republicans.

“You have to bring it to a closure sometime long before the end of August so that you can start that healing process and, you know, whoever wins can say their mea culpas about what they said, and bring the party back together,” he said on “Fox News Sunday.”

Massachusetts Sen. John Kerry, an Obama supporter who was the party’s losing presidential nominee in 2004, said the superdelegates needed to make up their minds early so Democrats can organize to beat McCain.

“As a former nominee, I will tell you, this time right now is critical to us,” he said on ABC’s “This Week. “I think every day does give John McCain an ability to organize nationally.”

(Additional reporting by Matt Bigg in Pennsylvania; writing by David Wiessler and Christopher Wilson; editing by Patricia Zengerle)