Johnson was born in a log cabin near St. Peter, Minnesota, on July 28, 1861, to Swedish immigrant parents. His father’s alcoholism forced his mother to provide for the family by working as a washerwoman. Young John assisted her by delivering laundry, working in a grocery store, and, after becoming a pharmacist in his early twenties, financially supporting his mother and younger siblings. In 1887, he bought part interest in the St. Peter Herald, a Democratic Minnesota newspaper, and served as its editor. He was active in the community’s civic organizations and Presbyterian church. He married Elinor Preston in 1894; they had no children.

Johnson was elected to the Minnesota State Senate in 1898, but lost reelection four years later in the heavily Republican district. He gained national attention in 1904 when he won the governorship running as a Democrat in the traditionally Republican state that gave President Theodore Roosevelt a two-to-one majority. As governor, Johnson earned a reputation as an honest and talented administrator free from ties to political machines or corporate interests. Working with a Republican legislature, he acquired a record of moderate reform, including laws for workers compensation, railroad regulation, and the election of state judges. In 1906, he ran an energetic campaign throughout the state, delivering 119 speeches and winning reelection by a landslide.

In July 1907, Harper’s Weekly profiled him in a series on five possible Democratic presidential candidates, and Louisville Courier-Journal editor Henry Watterson became his major promoter, seeing him as an electable alternative to Bryan. In early 1908, Johnson topped the New York World’s list of 16 candidates better suited for the Democratic presidential nomination than Bryan. Popularity in his home state and favorable national press were not enough, however, for him to overtake Bryan, who by the end of June 1908 had amassed more than the requisite two-thirds of the delegates needed for nomination. Although Johnson’s presidential candidacy ended, he won reelection to the governorship that fall. On September 21, 1909, he died after intestinal surgery.