MINNEAPOLIS — Amy Klobuchar, the third-term Minnesota senator, entered the race for the Democratic presidential nomination on Sunday, hopeful that her moderate politics, Midwestern roots and carefully cultivated history of bipartisanship can appeal to a broad swath of voters in contentious times.

On a snow-covered stage in Minneapolis along the banks of the Mississippi River, with the temperature barely above single digits, Ms. Klobuchar said that as president she would “focus on getting things done” and reverse some of President Trump’s signature policies. On her first day in office, she said, the United States would rejoin the Paris climate agreement.

“For too long, leaders in Washington have sat on the sidelines while others try to figure out what to do about our changing economy and its impact on our lives, what to do about the disruptive nature of new technologies, income inequality, the political and geographic divides, the changing climate, the tumult in our world,” she said.

“Let’s stop seeing those obstacles as obstacles on our path,” she continued. “Let’s see those obstacles as our path.”

“Minnesota matters, Wisconsin matters, Nebraska matters, Ohio matters — and, yes, Iowa matters,” she told the Iowa Farmers Union in December.

Ms. Klobuchar grew up in the Minneapolis suburbs as the daughter of a schoolteacher and a columnist for The Minneapolis Star Tribune. After graduating from Yale and the University of Chicago Law School, she returned to Minnesota to work as a corporate lawyer. The birth of her daughter, who was born with a condition that required her to remain in the hospital, plunged her into political activism. Ms. Klobuchar pushed for legislation that would guarantee new mothers a 48-hour hospital stay, a proposal that eventually became federal law. She was elected prosecutor for the state’s most populous county in 1998 and became the first elected female senator from her state in 2006.

In the Senate, Ms. Klobuchar has cultivated a worker-bee persona, not leading on divisive issues like immigration and focusing instead on curbing the cost of prescription drugs, addressing sexual harassment and protecting online privacy. A 2016 analysis found that she had passed the most laws of anyone in the Senate.

Ms. Klobuchar rose to national prominence during the Senate Judiciary Committee hearing for Justice Brett M. Kavanaugh, when she pressed the nominee on whether he had blacked out drinking. “Have you?” he shot back, to which she calmly replied, “I have no drinking problem, Judge.”

“When I turned on the TV and watched that hearing, I was so damn proud she was our senator,” said Gov. Tim Walz, one of several Minnesota officials who spoke at Ms. Klobuchar’s event.

After she took the stage to chants of “Amy,” Ms. Klobuchar reminisced about her family ties to northern Minnesota’s mining-centric Iron Range. The region, once a Democratic stronghold, has remained supportive of Ms. Klobuchar even as Mr. Trump and other Republicans have made inroads.