Well let's see. The election coming up is a general election. There are two choices.
Candidate A (Roberts) is 100% pro-life, pro-traditional marriage, pro-gun, anti-Obamacare, anti-illegal, has a 90% overall conservative record, ranked as the third most conservative member of the entire U.S. Senate, and was one of only handful of Senators (around a half dozen or so) who have ALWAYS stood with Ted Cruz, including during his filibuster when most of the Senate GOP caucus caved.
Candidate B (Orman) is pro-abortion, pro-gay marriage, pro-illegal, supports "reasonable" gun control, won't commit to repealing Obamacare, opposes the SCOTUS Hobby Lobby decision because it "gave corporations the same rights as people", has donated thousands of dollars to Barack Obama and Hillary Clinton, ran as a Democrat in 2008, and polling analyst Nate Silver estimates a 75% chance that Orman will caucus with the Democrats and put Harry Reid in charge of the Senate's agenda.
Sarah Palin endorsed Candidate A.
Seems pretty obvious to the rest of us why she did so.