The hard-fought U.S. presidential campaign was briefly put on hold Friday as all three White House hopefuls paid tribute to the late civil rights leader, the Reverend Martin Luther King, Jr. VOA National correspondent Jim Malone reports from Washington.

Friday marked the 40th anniversary of King's assassination at a motel in Memphis, Tennessee.

The man seeking to become the first black U.S. president, Senator Barack Obama, spoke about King's legacy during a campaign stop in Indiana.

"To recognize that no matter what color of our skin, no matter what faith we practice, no matter how much money we have, no matter whether we are a sanitation worker or a United States Senator, we all have a stake in one another," he said. "We are our brother's keeper, we are our sister's keeper."

Obama's Democratic rival, Senator Hillary Clinton, traveled to Memphis to mark the anniversary of King's death, as did the presumptive Republican presidential nominee, Senator John McCain.

Clinton is seeking to become the first woman president and paid tribute to King's efforts to bring about racial equality.

"Because of him, after 219 years, 43 presidents who have been white men, this next generation will grow up taking for granted that a woman or an African-American can be president of the United States of America," she said. "But as far as we have come, we know the journey is far from over."

Senator McCain spoke outside the motel where King was slain, which now houses a museum on the civil rights movement.

McCain said the Reverend King seems a bigger man now than he did 40 years ago and praised the quality of his character.

McCain also acknowledged he made a mistake when he initially opposed the creation of a national holiday on King's birthday to honor his legacy.

"When I voted against a federal holiday in memory of Dr. King, I was wrong," he said. "We can all be a little late sometimes in doing the right thing, and Dr. King understood this about his fellow Americans."

McCain has the luxury of preparing for the November election while Democrats Obama and Clinton continue to battle for their party's presidential nomination.

But a new nationwide poll suggests U.S. voters are in the mood for change as the election approaches, and that could be sobering news for McCain and congressional Republicans in general.

A New York Times-CBS News poll found that 81 percent of those surveyed now believe the United States is headed in the wrong direction.

"Four out of five, 81 percent, say the country is on the wrong track," said Kathleen Frankovic, director of surveys for CBS News. "Just 14 percent say it is headed in the right direction. That number, 14 percent, is the lowest number we have ever seen in the 25 years since CBS News began asking Americans to tell us if the country was on the right track or the wrong track."

The same poll also suggested softening support for Obama in his race with Clinton, and that the recent controversy surrounding inflammatory statements by Obama's former pastor may be having an impact on the race.

The survey showed Obama leading Clinton nationally by a margin of 46 to 43 percent. That is well down from Obama's lead of 54 to 38 percent in late February.

The poll also showed both Democrats ahead of McCain in head to head match-ups. Obama ran ahead of McCain by 47 to 42 percent, while Clinton led McCain by 48 to 43 percent.

McCain is beginning to focus on his search for a vice presidential running mate while the next major test for the Democratic contenders is the Pennsylvania primary on April 22.