Updated

Lance Mackey set off Sunday on the competitive portion of the 1,100-mile Iditarod Trail Sled Dog Race, armed with a serious mission — to repeat history by again winning two grueling back-to-back races.

There was so much to do — gear to check, sleds to pack — before the defending champion and a record field of mushers launched their run to Nome. But while other top contenders were somber, even terse with onlookers, the Fairbanks resident was relaxed and joking, with seemingly all the time in the world to spend with fans.

Maybe that's because Mackey is fresh off his fourth consecutive win in the 1,000-mile Yukon Quest International Sled Dog Race — considered by many to be an even tougher long-distance sled dog race. He said he felt more prepared than ever for the Iditarod.

Last year, Mackey became the first musher to sweep the Quest and Iditarod..

Mackey said he was a little nervous going into the Iditarod last year, but not now.

"People might expect me to do well here. As far at that goes, there is nobody putting pressure on me except for me," the 37-year-old throat cancer survivor said as well-wishers flocked around him on the frozen Willow Lake two hours before the clock started ticking in the run to Nome.

Cim Smyth of Big Lake was the first musher out of the chute Sunday afternoon. Jessie Royer of Fairbanks and Jim Lanier of Chugiak were the second and third mushers out.

Mackey, who was fifth, is trying for another Iditarod win. He said he considers mushing his job and if he doesn't do it well, he will be forced to get a "real job" to support his wife and family. He'd rather keep mushing.

"I am pressuring myself basically to do well. If I don't win this race again, I won't be disappointed," he said. "I can't complain at all, not even a little bit."

Six past winners and other top contenders are among a record field of 95 mushers, promising a highly competitive race over some of Alaska's most unforgiving terrain. The world's longest sled dog race kicked off Saturday with a short ceremonial run through Anchorage.

Rudi Niggemeier, a 51-year-old car dealer from Salzkotten, Germany, is among 33 rookies in the race. He's run other races, but the longest was only 300 miles. After spending five winters in Alaska, however, running the Iditarod became a goal.

"Now I feel it is time to go to Nome," he said. "I'm not a young man, but I'm only a little nervous."

The Iditarod, begun in 1973, commemorates a run by sled dogs in 1925 to deliver lifesaving diphtheria serum to Nome.

The modern-day Iditarod trail crosses desolate tundra, thick forests and two mountain ranges along the frozen Yukon River, then goes along the dangerous sea ice up the Bering Sea shore to the finish line in Nome. Temperatures can plunge far below zero and wind can wipe out visibility for the teams.

Mushers are competing for a piece of an $875,000 purse, to be paid out among the top 30 finishers to reach Nome. The winner gets $69,000 and a new truck worth $45,000.