The 200 free is a race Phelps dearly wants to win after finishing third four years ago in Athens. He lost to Aussie rival Ian Thorpe and Dutchman Pieter van den Hoogenband in what was billed as the "Race of the Century."
Now, Thorpe is retired and van den Hoogenband has dropped the event to focus on the 100 free.
A victory would give Phelps his ninth career gold medal, tying him with four others including Spitz and track star Carl Lewis, for most Olympic golds.
Phelps earned his second gold medal of these games with a world record in the 400 free relay. He, Garrett Weber-Gale, Cullen Jones and Lezak won in 3:08.24, nearly 4 seconds better than the old mark the Americans had set in Sunday night's prelims.
"Unbelievable," said Phelps, who set an American record leading off, 47.51. "Jason finished that race better than we could even ask for. I was fired up. Going into that last 50, I was like, 'Aw, this is going to be a close race.' Jason's last 10 or 15 meters were incredible."
Watching on deck, Phelps let out a roar that nearly cost him his voice and thrust both arms in the air.
"I've never celebrated that much after a race in my life," he said. "It's hard to put that kind of race behind you, but it sets me up for something good tomorrow. The 200 free final, that's my first priority."
After the 200 free final, Phelps will swim the 200 butterfly semifinals Tuesday morning, going in as the leading qualifier. His prelims time of 1:53.70 lowered his own Olympic record of 1:54.04 set four years ago.
Phelps was third after the first 100 meters, moved up to second at the 150, and then cruised home.
"The events are getting shorter and shorter," he said. "I started off with the hardest one. I'm just out there to swim and have fun, and that's what I'm doing."
Laszlo Cseh of Hungary, silver medalist behind Phelps in the 400 individual medley, was second-quickest in 1:54.48. Also moving on was China's Wu Peng and American Gil Stovall.
American Katie Hoff was just as busy as Phelps, swimming three races Monday, including two in the evening.
She qualified fourth for the 200 free semifinals, touching in 1:57.20.
Federica Pellegrini of Italy led the way with a world-record time of 1:55.45. Sara Isakovic of Slovenia was second and Caitlin McClatchey of Britain third. Also advancing was American Allison Schmitt in seventh.
"It's a great comeback after the disappointment from this morning," said Pellegrini, who was fifth in the 400 free. "I showed that I'm still in form. This morning I read the race wrong."
Earlier, Hoff was second-quickest in the 200 IM prelims with a time of 2:11.58, trailing Alicia Coutts of Australia, who touched in 2:11.55.
"I feel good. I'm glad it's over," Hoff said. "Tomorrow is just semifinals and then I'm backing off."
Hoff began the day by earning a silver in the 400 free final, getting upset by Rebecca Adlington of Britain. Hoff already had a bronze in the 400 IM.
"I feel like I have less pressure now," she said. "I already have two medals."
American Natalie Coughlin qualified third-quickest in the 200 IM, an event she took up only recently.
"A lot of people are like, 'What in the heck are you doing in that?' but it's really nice to be in an event where there's no pressure on me and no one's expecting anything," she said. "It makes me feel like an age-group swimmer because I keep improving."
Stephanie Rice of Australia, the 400 IM champion, was sixth-fastest in the 200 IM prelims. Kirsty Coventry of Zimbabwe, the 400 IM silver medalist, was eighth.