Elections
Stevens moved back to Rochester Hills to run for the United States House of Representatives seat in Michigan's 11th congressional district, launching her bid to unseat two-term Republican Dave Trott on April 27, 2017. While his spokesperson initially called Stevens a "carpetbagger", Stevens argued that she was born and raised in Southeast Michigan, and had spent her early career working for Michigan. Trott announced his retirement in September 2017, making the 11th district an open seat. Stevens defeated state Representative Tim Greimel in the Democratic Party primary election and Republican businesswoman Lena Epstein in the general election. In August 2018, Stevens was named as part of the DCCC's Red to Blue program, which focused on flipping U.S. House districts by ousting Republicans, joining fellow Michiganders Elissa Slotkin and Gretchen Driskell. Hillary Clinton recorded a late robocall in support of her. Following the robocall, she moved from second place in pre-election polls to winning the election. Politico credited her robocalls for boosting Stevens's campaign. Stevens was also endorsed by President Obama, who called her a "critical part" of his administration's efforts to bail out the auto industry. Stevens's victory, and that of Elissa Slotkin in the neighboring 8th district, made it the first time since the 1930s that no Republicans represented Oakland County in the House.
Stevens and Colin Allred, both alumni of the Obama administration, were selected as co-presidents of the House Democratic freshman class of the 116th United States Congress.
An October 2019 town hall on curbing gun violence turned contentious as protesters at the Commerce Township gun club, where the event was held, interrupted Stevens and other lawmakers. Stevens said "This is why the NRA has got to go" in response to protesters repeatedly shouting "NRA" in reference to the National Rifle Association.
Stevens ran for reelection. She was unopposed in the Democratic primary. In the general election, she defeated the Republican nominee, Eric Esshaki, in a tighter race that saw early ad spending from Republican-allied Congressional Leadership Fund.
In a 2020 floor speech, she shouted over the gavel of her own party saying that she was wearing pink latex gloves "not for personal attention" but to make a point about COVID.
As a result of population loss, Michigan lost a seat in the House of Representatives. The 11th District lost its share of Wayne County and was safely Democratic. The home of fellow Democrat Andy Levin was drawn into the district, and Levin sought reelection there, despite the majority of his old district being in the newly-designated 10th Congressional District. Stevens, whose home in Rochester Hills was drawn out of the district, moved with her husband to a home in Waterford, opting to follow most of her constituents into the 11th and setting up a primary challenge against Levin. She reportedly outspent Levin by a factor of five. Much of her support was driven by the pro-Israel lobby, which had spent $3 million on her campaign by July. Other dynamics in the race included generational and gender dynamics in the aftermath of the Supreme Court's overturning the Roe v. Wade and Planned Parenthood v. Casey. Stevens defeated Levin, 60%-40%. Her campaign focused on protecting reproductive rights and her background as a proponent of Michigan manufacturing, the state's dominant industry. Her victory was aided by $5 million from EMILY's List-affiliated donors and by the American Israel Public Affairs Committee, which invested $4.3 million targeting Levin and hailed her victory as proof that "being pro-Israel is both good policy and good politics". AIPAC's ads did not mention its motivation for supporting Stevens.
Stevens won the general election against Republican Mark Ambrose with 61.3% of the vote.
Stevens was challenged by Ahmed Ghanim in the Democratic primary. She won renomination with 87.1% of the vote. In the general election, she won reelection against Republican Nick Somberg and Green Party candidate Douglas Campbell with 58.2% of the vote.
Stevens voted in March 2023 with Democrats to oppose legislation proposed by Republicans to ban transgender athletes from competing in women's sports.
Following Joe Biden's debate with Donald Trump in the 2024 presidential election, Stevens "unequivocally" supported Biden, saying, "I trust our president and know he is the one to finish the job". As Kamala Harris consolidated support as the new nominee after Biden dropped out, Stevens immediately endorsed her.