The Chairman of the State Senate Republican caucus has resigned without giving a reason. But a report in St. Louis this morning indicates the reason Senator Chris Koster (R-Harrisonville) has quit the post is because he’s going to become a Democrat.

Koster has news conferences in Columbia, Harrisonville, and St. Louis today that he says might transform the political landscape of Missouri.

The St. Louis Post-Dispatch says Koster has been calling his campaign donors to alert them of his plans. He had been considered a leading Republican candidate for Attorney General.