In the U.S. presidential race, both Democratic contenders have stressed party unity before two primary contests that could prove decisive in deciding which of the two will face the presumed Republican nominee, Arizona Senator John McCain, in the November election. VOA's Michael Bowman reports from Washington, Democratic hopefuls Hillary Clinton and Barack Obama both appeared on U.S. television two days before primary elections in the states of Indiana and North Carolina.

For months, Senators Clinton and Obama have waged one of the longest and hardest-fought primary battles in modern American presidential history.

Rhetoric between the two contenders has often been sharp, with Clinton at one point questioning whether Obama has demonstrated the credentials necessary to be commander-in-chief, while Obama has blasted the free-trade policies adopted by Clinton's husband, former President Bill Clinton.

Some Democrats have openly wondered whether the intense intra-party fighting will weaken the eventual nominee and dim the party's chances of capturing the White House.

Sunday, the two presidential hopefuls appeared to tone down the heavy criticism and focus on party unity instead. Clinton spoke on ABC's This Week television program.

"Both Senator Obama and I have made it very clear that we will have a unified Democratic Party going into the fall elections," said Hillary Clinton. "I have said that I would work my heart out for him [if Obama is the nominee]. He has said he would do the same for me [if I am the nominee]."

Obama struck a similar chord on NBC's Meet the Press program.

"I want a Democrat to win in November," said Barack Obama. "So even if Senator Clinton were the nominee instead of me, I would still be campaigning for Democrats."

Obama leads Clinton in pledged delegates won from primary contests as well as the popular vote of all who have cast ballots in the nominating elections so far. Many political analysts have suggested it would be virtually impossible for Clinton to overtake Obama in pledged delegates in the remaining contests.

Yet Clinton has won the last three contests held in large, populous states - two of which, Ohio and Pennsylvania, are considered must-win states for any Democrat to capture the White House in November. In addition, Obama has had to endure firestorms of criticism stemming from recent comments he made that were perceived as demeaning to working-class voters, as well as incendiary remarks by his former pastor.

The controversies appear to have eroded support for Obama in national polls. What remains to be seen is whether they will sway so-called super-delegates, Democratic Party elders who are not bound by primary election results and who also have a roll to play in deciding the eventual nominee.

To date, there has been no mass exodus of super-delegate support away from Obama.

Asked whether super-delegates should feel empowered to overturn the will of the voters expressed through pledged delegates, Clinton suggested the nomination battle is more than a numbers game.

"There are a number of factors that people look at," she said. "We have delegates selected by millions of people in primaries and delegates selected by a few thousand people in caucuses. When the process finishes in early June, people can look at all the various factors and decide who would be the strongest candidate."

Obama downplayed any suggestion that the recent controversies surrounding his campaign would torpedo his candidacy.

"I think the super-delegates are going to take a look, not at momentary snapshot polls [showing reduced support for Obama], but who has run the kind of campaign that can bring about change in America and can actually govern after the election," he said.

Most political observers say Obama remains favored to win Tuesday's primary in North Carolina, although by perhaps a smaller margin than had been anticipated just weeks ago. Recent polls in Indiana give a slight edge to Clinton.