Republicans chose Jeff Johnson on Tuesday to be their candidate for governor, betting that the mild-mannered political veteran is the party's best chance to unseat Democratic Gov. Mark Dayton in November.

Johnson, a Hennepin County commissioner from Plymouth, led a four-man field throughout the night and, with 99 percent of the counted, emerged victorious with 30 percent of the vote. Party endorsement helped propel Johnson past state Rep. Kurt Zellers, who finished in second with 23 percent. Former state Rep. Marty Seifert came in third, just ahead of businessman Scott Honour.

A beaming Johnson told supporters on Tuesday night that "Mark Dayton is a fairly popular incumbent and a lot of people are going to say it's going to be really hard to beat him, but we can do that." From a victory celebration at Digby's restaurant in Plymouth, he urged Republicans to unite around a vision that appeals beyond the party base and to raise a lot of money for his campaign.

Low-key by nature, Johnson has sold himself as a solid conservative who would push to lower taxes, cut state spending, grow jobs and advocate for a state "where every child has access to a great education … patients and doctors make their own health care decisions … and there is no longer anger or envy over income differences."

Dayton, who promptly called Johnson Tuesday night to congratulate him, now must prepare to defend the accomplishments of a busy four years in office as he seeks a second term.

"Minnesota's in a lot better shape now than it was four years ago," Dayton said Tuesday, noting the state's nation-leading employment rate. Dayton voted in St. Paul in the afternoon. He faced only token opposition in the primary, but with about 178,000 votes he got more votes than the four leading Republican contenders combined.

The low-spending GOP primary featured candidates who were reluctant to lay into one another and the contest did little to drive turnout. TV ads were scarce, and candidates struggled for funding and attention amid the distractions of a Minnesota summer.

Once Johnson's win became clear, Zellers consoled his children as well as supporters in a concession speech.

After the race was called, and before walking up for his concession speech, Zellers hugged his teary-eyed wife, Kim, and daughter Reagan. His son, Will, asked "What's the score?" Kurt responded, "More them, less us."

Zellers told the crowd, "I never in my wildest dreams at all thought that after growing up on a farm … in North Dakota I would be this close to running for governor of Minnesota." Of his future Zellers that at 44, "I'm a little young to hang up my cleats."

Honour issued a statement urging the party to unify behind Johnson as it attempts to defeat Dayton.

The GOP has said its top goal is to break Democrats' stranglehold on state government, where DFLers control not only the governor's seat, but every constitutional office and both bodies in the Legislature. Republicans say that kind of one-party rule has resulted in overly high taxes and excessive spending.

Johnson and his three opponents are scheduled to appear together at a Wednesday morning press conference at the Capitol.

Johnson's quiet demeanor is a notable contrast to Dayton's last challenger, Tom Emmer. A brash and gregarious state representative at the time, Emmer lost narrowly to Dayton four years ago. He mounted a political comeback Tuesday by winning the GOP nod for the Sixth Congressional District seat.

Johnson brings low-key style

But Johnson also tried to show a quirky side as a candidate, as in the campaign ad where he compared his teenage son's erratic driving to Dayton's leadership style.

Johnson, 47, was born and raised in Detroit Lakes. He and his wife, Sondi, have two sons, aged 15 and 11.

After law school, Johnson worked for several law firms and as an attorney for Cargill. In 2000, he was elected to the Minnesota House, where he served six years.

In 2006, Johnson was the Republican candidate for state attorney general. He lost to Democrat Lori Swanson by more than 250,000 votes. Two years later he was elected to the Hennepin County Board, representing several northwestern suburbs.

Johnson said Tuesday night he would stay on the County Board while he runs for governor. As a candidate, he frequently said his experience governing an urban county would help him appeal to Democrats and independents.

Alliance for a Better Minnesota, a DFL-allied group that will help spread the party's message in November, reminded voters that during the primary Johnson said if elected he would "go all Scott Walker on Minnesota," a reference to the conservative Wisconsin governor.

Raising money key for GOP

Fundraising will be an immediate priority for Johnson. While Dayton was sitting on $850,000 at the end of July, Johnson had about $120,000 in the bank.

Republican insiders predicted the donations would flow now that a challenger has come into focus.

"The race has been low profile, and I think once it becomes one person versus Mark Dayton, money will be there," said Ben Golnik, a GOP strategist not backing a specific primary candidate. "I think you'll see our donor community quickly coalesce behind the candidate."

To that end, two influential donors to the GOP, Stanley Hubbard and Tom Rosen, have already planned a major fundraiser on Aug. 20 for Johnson.

"Nice guy that he is, Governor Dayton has had his time as governor. He's had his chance, and I'll do what I can to help his opponent get elected," said Hubbard, the head of Hubbard Broadcasting.

Aides to Dayton said that beyond a few appearances at the Minnesota State Fair, the governor will mostly refrain from overt campaigning until after Labor Day.

Dayton sets three themes

Dayton's campaign says it will hit three main themes come Sept. 1: strengthening the middle class, improving education and making government more efficient. A fixture in Minnesota politics for more than three decades, Dayton for the first time in a long political career is asking voters for a second term. The 67-year-old governor has said November will be the last time he's on an election ballot.

Dayton's first term has been eventful. He battled Republicans during the shutdown, pushed public funding for the Minnesota Vikings stadium through a GOP-controlled Legislature, joined with new DFL majorities in 2012 to increase income taxes on the wealthy and boost spending on schools, signed bills legalizing gay marriage and medical marijuana and raising the minimum wage. He also oversaw implementation of Obamacare in Minnesota.

The governor said he's prepared for a debate with the GOP over taxes. "If you're making less than $250,000 a year, your taxes have probably gone down," Dayton said.

In other contested statewide primaries, DFL State Auditor Rebecca Otto easily withstood a high-profile challenge from Matt Entenza, who pumped nearly $700,000 of his own money into the race. Otto captured more than 80 percent of the vote. Entenza, a former state representative who finished third in the 2010 gubernatorial primary, infuriated many Democrats with his last-minute campaign and harsh criticism of the incumbent.

In the GOP attorney general's race, the endorsed candidate, state Sen. Scott Newman, beat frequent candidate Sharon Anderson.

Star Tribune reporters Liz Sawyer, Maya Rao and Samantha Schmidt contributed to this report. Patrick Condon • 651-925-5049