Even senators who aren't running this year are staying involved in the fight for control of the chamber.

Senator John DeFrancisco is retiring at the end of this year, but he did endorse the Republican candidate running for his seat and the GOP's candidate in the 53rd district, where incumbent Senator Dave Valesky was defeated in the Democratic primary last month and then seemed to be getting support from Republicans to run as an independent.

Valesky ultimately decided not to continue his campaign- and that prompted DeFrancisco to push for voters to try to flip the seat.