Chris Benjamin, who until recently was a top  Republican aide in the Missouri House,  is expected to announce next week that he will run for the state Senate  – as a Democrat.

Benjamin will make an announcement on Monday, according to state Sen. Chris Koster, who will accompany Benjamin on a campaign swing. Koster said Benjamin will seek the 31st District seat in western Missouri that Koster is vacating to run for attorney general.

Benjamin, a lawyer, was  chief of staff to House Speaker Rod Jetton, R-Marble Hill, until late last year. Neither Benjamin nor Jetton could be reached Thursday.

In switching parties, Benjamin would follow a path set by Koster, who became a Democrat in August.  

Benjamin “comes from a labor family, has working class roots,” Koster said. “And I think he believes that the right wing of the Republican Party has shifted too far and has lost its ability to center itself.”

The 31st District is often viewed as a swing district. It was represented for years by conservative Democrat Harold Caskey.

Rep. David Pearce of Warrensburg is expected to seek the Republican nomination for the seat.