"Because you voted for change in November, we're going to bring change," he told the near-capacity crowd that had gathered in the 20,000-seat basketball stadium at the University of Maryland for the rally, some of whom had been waiting since before sunrise to hear the president speak.
The United States was "on the cusp" of fulfilling the promise of easier access to higher education, which is very costly, and of changing the health care system, which Obama said was a defining issue for the current generation.
"One in three adults who don't have health insurance live one accident away from bankruptcy," the president said, his speech regularly interrupted by deafening cheers and at one point by a lone heckler, who shouted "child killer" as Obama began his speech.
The president never broke his stride, and the heckler was quickly ushered out of the stadium by security guards.
The rally was the latest sign that Obama is now hitting back hard at opponents to his proposed reforms who hogged the media spotlight last month by disrupting town hall meetings held to explain and promote the president's vision for change.
It was also a bid by Obama's behind-the-scenes team, whose near flawless handling of his campaign took him from the bottom rungs of the US Senate to the White House, to boost the president's popularity ratings.
Obama's poll numbers have fallen over the past few months as politicians dickered over health care and the public reacted to what it saw as excessive government spending.
"It's time to put our shoulders to the wheel of history," Commerce Secretary Gary Locke, acting as a warm-up man for the president, told the exuberant crowd inside the University of Maryland's 20,000-seat basketball stadium before Obama arrived.
"We are closer than ever before to building a health care system that America can be proud of. We cannot let this opportunity slip by," he said as the crowd whooped and cheered.
A digital display on a blue tickerboard reading "Stable and Secure Health Care" ran across the uppermost level of bleachers on three sides of the stadium.
Rachel Peck, a third-year student at the university who was diagnosed in her first year with thyroid cancer, told the crowd: "It is for people like me, people like you, and millions across the United States that we have to address health care reform now."
Jean Silver-Isenstadt, president of the National Physicians Alliance, had come with her husband Ari, a pediatrician based in Baltimore.
"A solid majority of doctors support the public option," Silver-Isenstadt told AFP, citing the results of a survey published last week in the prestigious New England Journal of Medicine (NEJM), which showed that 62.9 percent of physicians back having a government insurance plan as part of Americans' health care coverage.
Just over 27 percent wanted only a private system, the poll showed.
"We're here to show our support for health care reform this year. The need is really urgent," said Silver-Isenstadt.
"So many patients have no access to coverage and can't afford it. The idea that this is something we can hold off on is unacceptable," she said.
The university band played an incongruous mix of songs -- Barry Manilow's "Copacabana," "Viva Las Vegas," "Sweet Caroline," "Living on a Prayer" -- as the crowd danced and chanted slogans from Obama's campaign.
Obama harnessed the energy by recalling how, back when "nobody could pronounce my name," his campaign hooked onto a slogan -- "Fired up, ready to go."
At the University of Maryland, after Obama stoked the passions of his supporters, some in the crowd filed out of the arena chanting, "Fired up! Ready to go!"