Due to Missouri's term limit rules, Davis was ineligible to run for the House seat again in 2010. She lost a Republican primary race for state senator in 2010, receiving 12,494 votes, or 45.4%. Davis left the Republican party in July 2011, joining the Constitution Party. In a letter to the Republican Central Committee she cited among her reasons for making the switch were pandering over principles, government of the highest bidders, and blocking fair party nominations. Further, she claimed that both the Republican and Democratic parties had "become destructive to our rights and freedoms". Speaking on her party switch, according to Davis, Democrats and Republicans have locked into a vicious cycle of abuse and "..both have treated us with what is known as the battered wife syndrome, when people get beaten up and before the court date they kiss and make up and everybody is happy again. Then they get to court and police officers have documentation that they saw the broken window and the body go through the window, they have pictures of the black eye and the fat lip and the broken arm, but by the time the court date comes, like my grandmother would say, ’tweren’t nothing'".