MINNEAPOLIS — Candidates made last-minute pushes to try to encourage their supporters to vote in Minnesota’s primary election Tuesday as low turnout made outcomes hard to predict in key races.

In the state’s most closely watched races, three Democrats were vying to challenge first-term GOP U.S. Rep. Chip Cravaack in northeastern Minnesota’s 8th District, while two Republicans sought the nomination to challenge incumbent Democratic Rep. Tim Walz in southern Minnesota’s 1st District.

There were no marquee statewide races. U.S. Sen. Amy Klobuchar faced token opposition in her Democratic primary, and Republican Kurt Bills didn’t face a major challenger on his side.

Secretary of State Mark Ritchie predicted turnout of less than 15 percent of eligible voters, and without the crowds of November, things were going smoothly around the state.

“Everything seems to be in order and all systems are go,” Ritchie said.

In the 8th District, former state Sen. Tarryl Clark started Tuesday at the Hibbing Taconite plant and chatted with voters in Virginia and Eveleth before voting in Duluth, where her stops included a Chamber of Commerce luncheon.

Former Duluth City Councilor Jeff Anderson began his day at the Minntac mine in Mountain Iron before campaigning and voting in Duluth. He planned to greet workers at a paper mill later in the day.

Former U.S. Rep. Rick Nolan ditched plans to be in Duluth and concentrated his efforts around his home base of the Brainerd area.

All three painted themselves as having the best chance of unseating Cravaack, a conservative newcomer who upset longtime Democratic Rep. Jim Oberstar two years ago in what had been considered safe territory for the party.

Clark and Nolan turned up the negativity recently, with Clark running a TV ad last week that accused Nolan of “blatant misuse of taxpayer dollars” as head of the Minnesota World Trade Center more than two decades ago. Nolan struck back, calling her ad “gutter politics.” Anderson’s campaign hoped to benefit from voters turned off by the attacks.

In the 1st District, state Sen. Mike Parry made the rounds to coffee shops and other places in Waseca and Owatonna, while former state Rep. Allen Quist did media interviews.

The rural 1st can be swing territory, but Walz is seen as a formidable candidate come November. Parry and Quist didn’t help themselves by tearing into each other after trading over-the-top comments. The week before the election, Parry was sharply criticized after accusing Gov. Mark Dayton, a Democrat, of popping pills in a meeting.

Even in the 8th and the 1st, the vote was slow.

Duluth City Clerk Jeff Cox said voter traffic was less than it was two years ago, when there was a hotly contested gubernatorial primary.

“Probably one step above light is the turnout at the moment,” Cox said.

On the Iron Range, Virginia City Clerk Lois Roskoski said turnout in her city was no more than 9 percent by midday, compared with about 18.5 percent four years ago.

In southern Minnesota, Blue Earth County Elections Director Patty O’Conner said the best turnout she had heard by late morning was a Mankato precinct that had seen all of 30 people. Olmsted County, home to the big population center of Rochester, reported the same.

The House and Senate races weren’t alone on the ballot. Forty legislative primaries were under way, including three western suburban Twin Cities districts where Republican incumbents faced conservative challengers.

It’s only the second time Minnesota has held its primary election in August since moving it up from September to give military and overseas voters more time to vote in the general election. But it’s the first since the state redrew its congressional and legislative district boundaries to reflect population shifts.

Also up were two Minnesota Supreme Court races, where the top two vote-getters will advance to the November election.