Senator Edward M. Kennedy waves to delegates as he takes the stage at the Democratic National Convention in Denver. In the back is his niece, Caroline Kennedy. (Ron Edmonds/Associated Press)

There was a huge outpouring of emotion for Ted Kennedy at the Democratic National Convention Monday night as the ailing senator took the stage and addressed the crowd.

Many delegates wiped away tears as Senator Edward M. Kennedy, who has a malignant brain tumour, gave a familiar wave and began to speak with a firm voice.

"My fellow Democrats, my fellow Americans, it is so wonderful to be here," he said. "And nothing, nothing is going to keep me away from this special gathering."

"I pledge to you that I will be there next January on the floor of the United States Senate," Kennedy said, drawing loud cheers and applause.

"The hope rises again, and the dream lives on," he said after his seven minutes at the microphone, as delegates waved thousands of Kennedy signs.

The 76-year-old party icon surprised many by making the trip to Denver from his home in Massachusetts on Sunday night. But it wasn't known until the last minute whether he'd be strong enough to make it from his hotel room to the convention.

Attack ads emerge as convention begins

The convention got underway Monday afternoon with a call to order by Howard Dean, the party's national committee chairman.

Democratic presidential candidate Barack Obama gets on a plane in Chicago, hours before the Democratic National Convention was set to begin in Denver. (Alex Brandon/Associated Press)

The four-day convention is designed to bring unity to the divided Democratic party as it officially names Illinois Senator Barack Obama as its presidential nominee.

Close to 50,000 delegates, journalists and volunteers are expected to attend in Denver's Pepsi Center arena while millions will be watching on television.

In the hours leading up to the event, the Republicans and Democrats set a fiery tone by unleashing scathing attack ads.

Obama and his team released a television advertisement focusing on rival John McCain's earlier admission that economics wasn't his best subject. The ad goes on to show McCain, the Republicans' presidential nominee-to-be, hugging President George W. Bush.

"Do we really want four more years of the same old tune?" the ad asks.

McCain's team, meanwhile, released an ad focusing on Obama's lack of support among Democrats who wanted New York Senator Hillary Clinton picked as the party's presidential nominee. She was in a tight race with Obama during the primaries earlier this year, but ultimately failed to draw enough support. She withdrew from the race June 7.

In the Republican ad, a Clinton supporter is quoted saying: "A lot of Democrats will vote McCain."

Obama team woos Clinton supporters

The Republican ad touches on a raw nerve for the Obama campaign, as polls suggest that some Clinton supporters are still not willing to back Obama and his vice-presidential choice of Joe Biden, a senator from Delaware. Pro-Clinton rallies are being planned to coincide with the convention.

Michelle Obama, her brother, Craig Robinson, and her seven-year-old daughter, Sasha, do a sound check at the Pepsi Center arena in Denver Monday afternoon. Obama and Robinson addressed the Democratic National Convention Monday night. (Ron Edmonds/Associated Press)

But Obama's team is dismissing the threat of Clinton supporters and rumours that Democrats are badly divided. Clinton herself is scheduled to speak at the convention on Tuesday, while her husband, former president Bill Clinton, will speak Wednesday.

Hillary Clinton is expected to release the delegates she won in the primaries later in the week, and encourage them to support Obama.

"Now I understand that the McCain campaign is running ads trying to divide us," Clinton told New York Democrats at a pre-convention breakfast, according to the Associated Press.

"I'm Hillary Clinton, and I do not approve that message," she added, to laughter and applause.

Democrat strategists said the Republicans are making more of a Clinton-Obama divide than actually exists.

"Barack Obama and Hillary Clinton are working very, very well together," Democrat strategist Tony Welsh told CBC News.

"I think the Republican dream, if they could have anything, it would be that we spend a lot of time discussing the so-called rift between them, but it's not there…. When voters are actually making a decision about who's best to lead this country, I think our folks are going to side with Obama and Biden for sure."

To further improve goodwill, the Democrat committee agreed to restore full voting rights to delegates from Florida and Michigan. They had been stripped of their voting rights at the convention because they held primaries earlier than the Democratic Party rules allowed.

Michelle Obama delivers keynote speech

Opening night also featured a keynote speech by Obama's wife of more than 15 years, Michelle Obama. She was expected to give insight into the personal life that she and her husband share.

"They're hoping this convention brings to the American people the real Obama," said the CBC's Henry Champ, who is covering the convention.

"The idea is that Michelle will be humanizing the candidate, talking about his life not only in politics, but also the kind of man he is and why she, his wife, thinks he ought to be president."

Republicans have sought to portray Barrack Obama as an Ivy League-educated elitist who doesn't have firm roots in the U.S. His mother was from Kansas and his father was from Kenya, and he was raised in Hawaii and Indonesia.

But Obama has stressed that he comes from a middle-class background and went to Harvard and Columbia on scholarships. He has said he and his wife struggled to pay off student loans and pay for child care.

"Our stories are the quintessential American stories," Michelle Obama told CNN on Monday, according to AP. "I am here because of the opportunities that my father had, that my mother had. You know, we are who Americans were supposed to be."

Other speakers Monday night include Obama's sister, Maya Soetero-Ng, and Craig Robinson, his brother-in-law. The schedule includes a surprise speaker, former Iowa congressman Jim Leach, a Republican moderate who broke ranks with his party this month and endorsed Obama.

Obama, who is campaigning in the Midwest and will not arrive at the convention until Wednesday night, will close the convention Thursday night at Denver's Mile High Stadium, where he will give his speech accepting the Democrats' nomination from the 50-yard line.

With files from the Associated Press