In a 30-minute speech met with calls of "Yes, ma'am!" and "Four more years!", she touted her husband's work on health-care reform, the auto industry bailout, ending the war in Iraq, and the economy.
Addressing a smaller but equally enthusiastic crowd of 1,800 at Upper Dublin High School in Fort Washington, Montgomery County, later in the day, she described how her father, a water plant pump operator, struggled to put her and her brother through college.
"My parents poured everything into me and my brother. Education was everything in our family," she said.
Turning to the presidential election, she asked: "Are we going to continue the change we've begun and the progress that we've made, or are we going to allow everything we've worked so hard for to just slip away? We need to keep moving forward."
Her visit, which included an evening stop in Bethlehem, Pa., came as the president stumped in Colorado, another state where his chances hinge on shoring up his 2008 coalition of young, minority, and female swing-state voters. The couple plan to campaign together next week in a third battleground state, Iowa.
Despite the struggling economy, Pennsylvania has leaned slightly in favor of Obama over Republican challenger Mitt Romney in recent polls. Success here is crucial to Democrats' hopes on Nov. 6 - and nowhere more so than in Philadelphia and its suburban swing counties.
Montgomery County, once a GOP stronghold, went for Obama in 2008. More recently, voters there elected their first Democratic-led county leadership in modern times.
And Michelle Obama remains one of the president's most popular advocates. Polls put her approval rating near 66 percent - compared with the mid-40s for her husband and his challenger as well.
Dressed in a simple print dress and pearl necklace, she eschewed discussion of weighty policy issues or of Romney in Fort Washington, peppering her remarks instead with glimpses of domestic life with their daughters Sasha, 11, and Malia, 14.
Julie Haywood of Cheltenham said she could hear echoes of her own life.
"I'm a working mom, I have three children, and I serve on the local school board," Haywood said. "But I make sure to find time every week to move this campaign forward."
Mentions of the Affordable Care Act - the Republican-derided health-care law that has become the signature of her husband's first term - and the president's commitment to women's health issues drew the loudest cheers.
But the GOP was already countering Thursday's appeal to women like Haywood. Massachusetts' former lieutenant governor, Kerry Healey, rallied female Romney supporters at an event in the city's Northwest section.
Replacing Obama would be a boon to women, who suffer as much as anyone in the so-called jobless recovery, Healey said. Her speech was part of a series of "Women for Mitt" meetings this week around the country.
"Half of our cabinet-level posts were occupied by women," Healey, who served with Romney when he was governor, said in an interview before the event. "His chief of staff was a woman. . . . His top policy adviser was a woman."
The power he entrusted to women "says a lot about who Gov. Romney is," Healey said, "and it's something that is not well-known."
Contact Jeremy Roebuck at 267-564-5218, firstname.lastname@example.org, or @jeremyrroebuck on Twitter.