A poll shows a tight race among four Republican governor candidates heading into Tuesday’s state primaries.

Capitol 5 featA survey commissioned by the St. Louis Post-Dispatch reveals all of them within five percentage points of each other.

Businessman John Brunner leads the pack with 23 percent support, followed by former Navy SEAL Eric Greitens and one-time state House Speaker Catherine Hanaway, who are tied at 21 percent.  Lt. Governor Peter Kinder has 18 percent.

Brad Coker with Mason-Dixon, which conducted the poll, thinks Democrats could try to rig the contest by voting in the Republican primary, a tactic thought to have been used in a previous Senate race.

“It was said some Democrats got together, and in order to help Claire McCaskill, took Republican ballots and voted for Todd Aiken” said Coker.  “On paper, he was by far the weakest Republican that she could’ve faced.  He kind of came from third place to first place in the final week of the campaign.”

Missouri has “open” primaries where anyone can vote in each party’s election.  Voters in the state do not register with any party.

Coker says the Republican contest is one of the tightest he’s ever seen.  “This is the first time I’ve seen it where you have four candidates.  I’ve seen it with three-way races before, where three candidates will all get clumped together within four or five points of one another.”

The poll also shows Democratic front-runner Chris Koster leading all the GOP candidates in a head-to-head battle.

Koster, who’s expected to easily win his party’s nomination, is ahead of Kinder by one point, Brunner by six points, Hanaway by 16 and Greitens by 18 points.

Coker thinks if either Brunner or Kinder can survive the primary, the general election will tie-up almost immediately, with Kinder possibly being favored after already having winning at the statewide level.

He says Kinder is hampered in the primary because he’s seen as the establishment candidate in a year it’s not desirable to be part of the Republican establishment, based on what’s happened in the presidential primary.