Here is where Sarah Palin’s endorsement of Trump could help him, especially in Iowa. She is very popular with Cruz’s strongest supporters.
The graph below shows how support for the tea party has been related to support for Trump, Cruz, and Palin. The data for Trump and Cruz come from two recent YouGov/Economist polls. The data for Palin come from the 2012 Cooperative Campaign Analysis Project, which was also administered by YouGov.
At least as of 2012, Palin was almost exactly as popular with tea party supporters as Cruz is now. The question is whether her endorsement helps win any tea party supporters over to Trump, perhaps even enough to ensure that he wins the Iowa caucus.
But there is a potential downside to Palin’s endorsement. She is not popular with the electorate as a whole (nor is Trump, for that matter). In fact, one piece of research found that Palin may have cost the Republican presidential ticket nearly 2 points in 2008 — a remarkable effect for a vice presidential nominee.
In short, Palin could conceivably provide Trump a short-term boost in Iowa, but her endorsement is not a credential he’d want to advertise if he becomes the nominee.
Michael Tesler is an assistant professor of political science at the University of California at Irvine. He co-author of “Obama’s Race” and author of the forthcoming “Post-Racial or Most-Racial? Race and Politics in the Obama Era.”