When the voters of Southern Minnesota shocked the Republican establishment in 2006 and elected a Democratic newcomer to represent their largely rural district, their new congressman, Tim Walz, repeatedly reached out his hand.

A former National Guardsman, high school teacher and football coach, Mr. Walz then sided with Republicans in the House over his five terms in office, earning a bipartisan reputation even as he largely voted along party lines. He received an A rating from the National Rifle Association. He voted yes on the Keystone XL petroleum pipeline from Canada, and supported tighter screening of refugees from Syria and Iraq. He opposed Obama-era regulations on wetlands and waterways, and voted no to bailing out banks and automakers in 2008 as the financial markets were in a tailspin.

He was elected governor in 2018, leaning into his small-town upbringing and the moderate credentials he had burnished in Washington.

But things changed in 2022 when the Democratic-Farmer-Labor Party, or D.F.L., took complete control of the state government. The centrist governor transformed into a hero of the progressive left, enshrining abortion rights into law, legalizing marijuana, enacting a statewide paid family leave program, offering drivers licenses to undocumented immigrants, tightening gun control laws and passing climate goals.

“No question he moved left as governor,” said Representative Dean Phillips, a Democrat who represents suburban Minneapolis and challenged President Biden for his party’s White House nomination.“But he’s a pragmatic moderate at heart.”

Mr. Walz’s record, first in the House, then as governor, is sure to be scrutinized as Vice President Kamala Harris’s newly-minted running mate. To Democrats in Minnesota, he is still that common-sense rural lawmaker, able to work with Republicans when needed, and willing to stand his ground when he must.