His position in the state Republican Party's leadership ranks makes him familiar to the activists who will endorse a candidate next year. He said he would abide by the party's endorsement, ruling out a primary bid if another candidate gets the GOP nod at its state convention.
Johnson has been on the governing board of Minnesota's most populous county since 2009 and was a three-term state legislator before that. He ran unsuccessfully for attorney general in 2006.
Dayton has said repeatedly he will seek a second term, which would be the first re-election campaign of his political career. Dayton said he's steering clear of taking on possible opponents for the time being.
"Ultimately the Republicans will decide who my opponent is and I'm not going to engage with anybody in particular until they've made their decision of who their candidate is going to be," Dayton said in late April. "We'll have a spirited contest, no doubt, and the people of Minnesota can decide if they want to keep me around or not."
Ken Martin, the chairman of the state Democratic Party, took a swipe at Johnson by characterizing him as "a classic politician trying to climb the ladder."
Republicans haven't done well in Minnesota in recent years. The party hasn't won a statewide race since Gov. Tim Pawlenty won a second term in 2006 in an otherwise washout year.
The governor's race field is almost certain to grow beyond the two GOP candidates already announced. Others said to be considering campaigns include: former House Speaker Kurt Zellers, Senate Minority Leader David Hann, state Sen. David Thompson, state Sen. Julianne Ortman, state Sen. Julie Rosen and Hennepin County Sheriff Rich Stanek.
Unlike Honour, who announced his candidacy in an online video, Johnson opted for the old-fashioned rollout in a community hall attended by family, friends and longtime supporters. But unlike his Republican rival, Johnson lacks the personal wealth that Honour has said he may use toward a campaign. Johnson made a plea for small-buck donations before leaving the stage at his event.
An employment lawyer by training, Johnson now works full time in the Hennepin County post.
He played up his upbringing in Minnesota, where he has spent nearly all of his adult life. He and wife, Sondi, have two sons with names reflective of Minnesota's Scandinavian heritage, Thor and Rolf.