Sen. Ron Johnson faces Democratic challenger Mandela Barnes in Wisconsin general election

Republican Sen. Ron Johnson of Wisconsin will defend his seat against Democratic Lt. Gov. Mandela Barnes in a swing-state face off that could become one of the most competitive races of the midterms.

Johnson breezed through the state’s Republican primary election Tuesday night, NBC News projected. Barnes was expected to have a tougher primary battle up until his top Democratic opponents dropped out late last month, clearing his path to the nomination, NBC projected.

Democrats have zeroed in on Johnson’s seat as they fight to hang onto their razor-thin Senate majority. The two-term incumbent, backed by former President Donald Trump, is the only Republican senator running for reelection in a state that President Joe Biden won in 2020. Multiple polls also show Johnson’s approval ratings underwater.

Johnson, 67, has also been a magnet for criticism from Democrats who say he has spread harmful conspiracy theories about the coronavirus and the integrity of the 2020 election, among other controversial remarks.

The Democratic Senatorial Campaign Committee has already spent money on primary-day attacks ads that accuse Johnson of working in Congress to benefit himself and wealthy donors at the expense of ordinary voters.

Barnes, 35, would become the youngest member of the Senate, as well as Wisconsin’s first Black senator, if he wins in November. He has been endorsed by well-known political figures including Sens. Bernie Sanders, I-Vt., and Elizabeth Warren, D-Mass.

Johnson’s campaign has lashed out at Barnes as a “career political activist” who is too far left for the purple state of Wisconsin, which Trump carried in 2016 and only narrowly lost in 2020. 

Barnes had been a community activist after college, and served in the Wisconsin State Assembly before becoming lieutenant governor. And he doesn’t shy away from progressive social issues: His TikTok account, for instance, features posts of him calling for the Senate to end the filibuster, codify Roe v. Wade into law and pass the Equality Act to enact protections for transgender people.

But Barnes’ campaign has largely focused on economic issues, highlighting his middle-class upbringing in Milwaukee and contrasting it with Johnson’s status as one of the richest members of the Senate.

More money is expected to flow into the race as the candidates barrel toward the November general election. Johnson’s campaign had raised more than $17 million by July 20, compared with $7 million raised by Barnes – though Barnes’ campaign said on Aug. 1 that it raised $1.1 million in just a week, after his Democratic rivals united behind him.

Meanwhile, super PACs for both sides of the race are already pouring millions of dollars into Wisconsin, Forbes reported.