No one would accuse Gov. Tim Walz of Minnesota of being flashy. He taught social studies for 20 years before trying politics. During six terms in Congress, he was regarded more as a workhorse than a showboat.

Neither has Mr. Walz really been a household name outside of Minnesota — at least, not until this past week, when he made a flurry of cable news appearances pointedly pressing Kamala Harris’s case and dismissing Donald J. Trump’s agenda as divisive and extreme. And weird.

“These guys are just weird,” Mr. Walz said on Saturday of the Republican ticket. He was talking to a crowd of canvassers for the Harris campaign in St. Paul, but the “weird” line of attack, which he has been using for months, went viral. (Ms. Harris herself used the words “just plain weird” over the weekend to describe the ways in which Republicans have chosen to criticize her.)

Weird is not a word most people would use to describe Mr. Walz, and that may well be one reason he is among a handful of Democrats under consideration as Ms. Harris’s potential running mate. Mr. Walz is seen as offering a steady, down-to-earth, everyman persona. His supporters say he also would bring a record of winning over moderate voters and deep roots in the rural Midwest that might serve as a counterpoint to JD Vance, Mr. Trump’s running mate.

Mr. Walz, 60, was raised in a small town in Nebraska. He attended public schools and graduated from Chadron State College in Nebraska. He taught at a public school in Mankato, Minn., a small city south of Minneapolis where Mr. Walz and his wife, a fellow teacher, raised two children. Outside of the classroom, he coached high school football and served in the Army National Guard for 24 years, ascending to the rank of command sergeant major.