It helps them determine whether an assertion made by one source is likely to be true.
FOR FARTHER EXPLANATION
Corroboration is the skill of comparing multiple sources regarding an event to find the most consistent and valid version of the event.
Political scientists would use corroboration to determine political results, polling, campaign progress, as well as bill development. A study on the passage of the Affordable Care Act for example would pull together versions of the bill as well as party opinions on the bill. In writing an assessment on the bill, the political scientists would look at all of the information and come to a conclusion.