A presidential ticket now in hand, exuberant Democrats flooded downtown Denver today for the official start of their 2008 nominating convention, hoping to heal rifts from a bruising primary season and begin their fight to the November election with renewed focus.

Security is tight, media lines into the Pepsi Center wax and wane, and a few protesters have already been arrested, all for a convention that is predicted to have a cast of characters that number close to 100,000.

Stores lining the streets near the convention greet attendees with signs offering "liberal discounts" and mannequins welcoming patrons in Obama '08 T-shirts.

Usually these highly choreographed political extravaganza leave little room for secrets.

But this year, details surrounding at least two last-minute surprises remain blurry and have delegates buzzing.

First, came word this morning that Sen. Ted Kennedy arrived in Denver to attend the convention. Kennedy was diagnosed with a brain tumor earlier this summer and taped a video message to be played at the convention, as he had planned to stay home.

"Senator Kennedy is in Denver and plans to attend tonight's tribute to him." Kennedy spokeswoman Stephanie Cutter told ABC News' Rick Klein on Monday. "He's truly humbled by the outpouring of support, and wouldn't miss it for anything in the world."

Cutter said for the moment, Senator Kennedy plans to attend, but not speak.

Democratic Convention Preparation

Then there is the question of Sen. Hillary Clinton's roll call vote. In an effort to soothe Clinton supporters, Clinton and Obama camps brokered a deal earlier this month to place her name into nomination with Obama's to be followed by a roll call vote. As of Sunday, it was unclear whether that would happen; some Clinton insiders told ABC News that there's fear that a roll call might disrupt the party's attempts at unity.

"The roll call is in flux," ABC News' George Stephanopoulos reported on "Good Morning America" today. On Sunday, House speaker Nancy Pelosi said she understood that the roll call vote would still be conducted.

An estimated 30 percent of Clinton supporters are still not ready to back Obama, polls show. "That's the difference between winning and losing for Barack Obama," Stephanopoulos said.

Speaking to the New York delegation breakfast in Denver this morning, Clinton stressed that Democrats are united, saying that word at least nine times in her remarks, per ABC News' Eloise Harper.

"We are gathered here in Denver for a very clear and simple purpose and that is to come out of this convention energized, excited and ready to elect Barack Obama the next president of the United States," Clinton said to a cheering crowd.

But this evening, Obama's wife, Michelle, will take the spotlight, delivering the first major address of the convention.

Aides say she will try to introduce her husband to the country by telling his life story as well as endearing anecdotes about their family so that everyday Americans can identify with him.

The candidate's wife will also showcase herself as a potential first lady who is one of them: She's a fan of the "Brady Bunch" and "Dick Van Dyke" reruns.

"It will be about the Obama family and the people who inspired them," Valerie Jarrett, a longtime friend of the Obama's and a key adviser, told "Good Morning America" today.

Obama the candidate will be watching his wife from Kansas City and will appear briefly live via satellite after she speaks.

He told reporters he is still working on his own speech for Thursday, and that it will sharply criticize his Republican opponent ,John McCain, something Democratic strategists say John Kerry should have done to President Bush during his acceptance speech four years ago.

"I am still tooling around with my speech a little bit," Obama said. "Hopefully, it'll make clear the choice that the American people are going to face in November."

Green Democrats and Party Bloggers

Those in attendance range from the expected lot of Democratic heavyweights (and reporters who cover them) to the hangers-on only a modern day political convention could producing.

"Obama button!" yelled Kevin Terry, 31, of Columbus, Ohio, to Democratic delegates as they walked by the Colorado Convention Center.

Also peddling Obama pins was John Cabrera, 50 of Columbus, Ohio, wearing a USA flag cowboy hat.

"I've been in town a couple days, and you can just feel the excitement building, and I'm excited to be here," he said. "I'm basically here trying make money, pay the alimony, have fun."

This year Democrats have credentialed 120 bloggers -- more than four times as many as the 2004 convention in Boston accredited.

Bloggers will have their pick this year of several lounges devoted to helping them get video, blogs and photos on the Web, including one sponsored by Google with free massages and smoothies.

There is also a YouTube uploading station for videos inside the Big Tent where liberals, including Markos Moulitsas, are scheduled to speak.

"Immediately after viewing a performance or presentation, bloggers can put it out immediately to the world on YouTube," said Aaron Nelson of the Alliance for Sustainable Colorado, one of the groups sponsoring the Big Tent program.

There's a push for a "green" focus: Democratic delegates are being encouraged to pedal around town instead of driving.

The Denver 2008 Convention Host Committee, Humana Inc., and Boulder-based Bikes Belong are providing 1,000 bikes for use by residents, visitors and delegates during the Democratic convention.

"We've provided a thousand bikes here in Denver, and we will again in the Twin Cities, that people can take out and ride for free during the convention and return them to any of the seven stations in Denver and in the Twin Cities," said Mitch Lubitz, Humana spokesman. Major carmakers are also lending hybrid and alternative fuel cars for delegates and members of the press.

Security Tight

A large anti-war protest disrupted access to the convention site for about 40 minutes Sunday afternoon with a crowd of about 1,000 protesters gathering in front of the Pepsi Center in Denver.

Anti-war protesters -- carrying signs reading "Send Them Home," "No War on Iran" and "Do-Nothing Democrats" marched in front of the convention site amid police in full riot gear.

"We're here to send a message to the American public and political candidates and party activists that we need to change course in this country. We'd like to see U.S. troops and military contractors all brought home from Iraq and Afghanistan," said Kevin Cross, 46, of Fort Collins, Colo.

Secret Service and local police locked down the security perimeter about noon, shutting down the only access point for media and most staff to get into or out of the site.

That left three PBS senior correspondents trying to get in for a television rehearsal standing outside the gate in the hot sun checking their watches.

"How long have we been standing here?" Margaret Warner asked her colleagues Gwen Ifill and Judy Woodruff in line. "Only five minutes," Ifill said.

"It feels like 20 minutes," Warner said. "We're late for a rehearsal."

Woodruff said that despite the security challenges, she was happy to be covering this year's convention.

It is a circus, but it's an important circus," said Woodruff, a PBS senior correspondent for "The News Hour With Jim Lehrer."

"To me there's something extraordinary about the American people having this opportunity once every four years to hear from one party for a week and then the other party," she said.

Reviving Faith in Party Politics for Election

Each night of the four-day affair offers a theme -- One Nation, Renewing America's Promise, Securing America's Future and Change You Can Believe In -- each including a range of speakers from Democratic politics past and present, helping to shape the party platform and charge to November.

But what impression will the Democrats leave?

Larry Sabato, director of the Center for Politics at the University of Virginia, has attended every political convention since 1976 and questions how much the dog-and-pony show matters to the American voter.

However, he said the Democrats' focus on the economy could go a long way in wooing working-class voters, who are key to winning November's battleground states.

"All the other issues and all the other symbols, they just pale in comparison. If people are unhappy enough about the economy they will change even if they are worried about the change," he said.

Last night at an interfaith service to kick off the convention, Rabbi Tzvi Hersh Weinreb, executive vice president of the Union of Orthodox Jewish Congregations, spoke about "our scared responsibility to our neighbor" -- the first official event Sunday of the 2008 Democratic National Convention.

"This highlights the importance that all faiths have in a Democratic society, and that religion has a role to play in many different ways," he told ABCNews.com.

(ABC News' Jake Tapper and Rick Klein contributed to this report)