Walz was on few people’s shortlist in the immediate aftermath of President Joe Biden’s withdrawal from the race, but he became a quick favorite from different sectors of the party for a spot on the ticket. Democrats hope that what they see as Walz’s folksy relatability will help with working-class voters — a constituency that connected with Biden, helping the president win back the “Blue Wall” states in 2020.

In the brief tryout period, Walz, who is little-known on the national stage, proved to be an effective communicator on behalf of Harris, according to her allies. He landed clear, cutting criticisms of former President Donald Trump and his vice presidential nominee JD Vance that went viral in recent weeks.

Significantly, Walz helped Democrats hone a new messaging frame, casting Republicans as “weird,” a put-down now regularly deployed by the Harris campaign.

“We start out as underdogs,” Harris said in her statement. “But I believe together, we can win this election.”

Walz has deep ties to communities Democrats have been bleeding support from for years. He grew up in a small town in Nebraska. He served more than two decades with the Army National Guard. He won a rural, conservative-leaning chunk of southern Minnesota in his 2006 bid for the House and held that battleground seat for over a decade, running as a moderate and bipartisan reformer focused on veterans’ issues.

But he’s also evolved with the Democratic Party, leaning into a progressive profile as governor and shifting his position on guns. When he first ran for Congress, Walz received an “A” rating from the National Rifle Association. But after the Parkland High School shooting in 2018, he denounced the NRA in an op-ed. As governor, he signed universal background checks and red-flag bills into law.

During his first term as governor, Walz confronted two major challenges: George Floyd’s murder in Minneapolis and the coronavirus pandemic. He faced criticism in his handling of both crises, including failing to deploy the state’s National Guard sooner to respond to the Floyd protests that set a police precinct ablaze and prolonged school closures during the pandemic. Republicans have already signaled that they plan to use Walz’s response to the pandemic against him.