The field of Republicans running, or planning to run, for Minnesota governor is getting crowded.

First there were two: Orono businessman Scott Honour and Hennepin County Commissioner Jeff Johnson, who jumped in early to challenge incumbent Gov. Mark Dayton. That number is about to double, as former House Speaker Kurt Zellers and state Sen. Dave Thompson prepare to launch their campaigns in the coming days.

Thompson, a two-term senator from Lakeville, will officially enter the race on Wednesday after filing his paperwork with the campaign finance board on Monday. "I am very much looking forward to bringing my message and having a conversation with the people of Minnesota."

Zellers, who led the House through two turbulent years of Republican control and frequent clashes with Dayton, is expected to announce his campaign Sunday afternoon. He did not respond to calls for comment.

Other Republicans weighing a run include 2010 gubernatorial candidate and former House Minority Leader Marty Seifert, state Sen. Julie Rosen, Senate Majority Leader David Hann and House Majority Leader Matt Dean.

Dayton, meanwhile, heads into his re-election campaign with his highest approval ratings since taking office — 57 percent in the most recent Star Tribune poll. He is fresh from a legislative session in which he successfully pushed for higher taxes on the wealthy, saw Minnesota become the 12th state to legalize same-sex marriage, and funded free all-day kindergarten statewide.

The governor, who was in Europe on a trade mission this week, has ramped up his fundraising schedule and begun to build his campaign infrastructure.

Dayton holds an advantage going in: Ousting a governor isn't easy.

Since 1960, four out of every five governors across the country who made it onto the November ballot have been re-elected.

The University of Virginia's Center for Politics ranks Minnesota's 2014 governor's race as a "likely Democratic" win.

Undeterred, Republicans are preparing to hammer the governor on the $2.1 billion package of tax increases that just passed the DFL-led legislature, as well the Democratic push to allow child care workers to unionize. They argue that the state's strengthening economy should be credited to the budget that passed two years, when their party led the Legislature.

"The fact that this is a race that Republicans can win seems to be confirmed by the number of folks interested in throwing their hat in the ring," said Minnesota Republican Party Chairman Keith Downey.

There is no formula for a perfect gubernatorial candidate, but Downey said the most viable candidates are a good fit for the office they seek, have enough name recognition to go up against a sitting governor in a crowded field, and bring the right reputation, credentials and values to the race.

"Number one, you have to be totally honest with yourself," Downey said. "If you're strong in all three of those areas, you're a great candidate. If you're strong in two of them, you can probably win. If you're only strong in one of them … you have to ask yourself whether you have a realistic chance."

Rosen readies

If Rosen enters the race, she's poised as a formidable threat. Independently wealthy, with strong ties to the business community, the Fairmont Republican has a reputation for working across party lines. She was a leader in the effort to build a new Vikings stadium and has worked across the aisle on many health and human services initiatives.

A source close to Rosen said she is 95 percent certain she will run, with an announcement to come in the next few weeks.

Honours on Friday announced a campaign finance committee bristling with CEO-types and business leaders. He's hoping his nonpolitical background will work to his advantage. "I'm not a career politician, which I think is a positive and I think it's needed," Honour said.

Zellers may not be talking about his race yet, but he's taken all the steps to prepare for it, including buying up campaign domain names like zellersforgovernor.com.

Zellers has connections within the state Republican establishment and may have the best name recognition in the potential candidate field. But that high profile cuts both ways.

His budget battle with Dayton sparked a three-week government shutdown in Zellers first year in leadership. His final year as speaker was capped by two divisive constitutional amendments and an election that cost Republicans control of the Legislature. He angered both supporters and opponents of the new Vikings stadium by voting against funding the construction, but allowing the stadium bill to pass anyway.

Thompson, an attorney and former radio show host, has long visited Republican gatherings all over the state and quickly cut a prominent profile among lawmakers when he arrived at the Capitol in 2010.

Hann, a four-term state senator from Eden Prairie who ran for governor in 2010, will decide soon, based in part on the health of his wife, who recently completed cancer treatment. She recently got "a clean bill of health," Hann said.

Former House Minority Leader Seifert is still weighing his options, saying "I haven't ruled out running." The Marshall Republican lost a 2010 GOP gubernatorial endorsement bid, but could restart his old campaign apparatus and tap into the base of support that led him all the way to the 2010 state convention.

Staff writers Baird Helgeson and Rachel E. Stassen-Berger contributed to this report.

Jennifer Brooks • 651-925-5049