A couple of weeks ago, few Democrats could have identified Gov. Tim Walz of Minnesota.

But in a matter of weeks, Mr. Walz has garnered an enthusiastic following in his party, particularly among the liberals who cheer on his progressive policies and relish his plain-spoken attacks on former President Donald J. Trump.

That support helped him become Vice President Kamala Harris’s running mate. Here’s a closer look at Mr. Walz.

Where did he get his start in politics?

Mr. Walz grew up in rural Nebraska. He served 24 years in the Army National Guard and retired as a command sergeant major. He received a social science degree from Chadron State College in Nebraska.

Mr. Walz met his wife, Gwen, while the two were teachers. They have two children.

Mr. Walz had been teaching high school social studies when he decided to run for office. In 2006 he knocked off a Republican incumbent, a rare feat, in Minnesota’s First District, a rural area that leans Republican.

Mr. Walz spent six terms in the U.S. House before he was elected governor in 2018. He won by more than 11 percentage points, propelled by voters in the cities and the Minneapolis suburbs. He ran again and won in 2022.

What are his top issues?

The political landscape has become more favorable for Mr. Walz during his second term as governor. Democrats flipped the State Senate, giving them control of both chambers of the State Legislature.