In American jurisprudence, a criminal prosecution has a high burden of proof, and that is because a defendant’s life or liberty is in jeopardy. A civil suit has a much lower burden of proof than a criminal case, because it is only a defendant’s property that is in danger of forfeiture. In both situations, there is a presumption of a defendant’s innocence, and a requirement of due process, because something to which someone has a constitutional right is in jeopardy.
In the case of someone who has been nominated to serve in a public office, there is no right of entitlement whatsoever. Denying a nominee to a public office confirmation to that office does not deprive that person of either life, liberty, or property. Consequently, in evaluating a person’s fitness for public office, there is no requirement of a presumption of innocence. A candidate for public office is not on trial, and the burden of proving their fitness for office and qualifications is upon the candidate and not upon those tasked with evaluating their worthiness.
Interestingly, those who argue that Brett Kavanaugh is entitled to due process and a presumption of innocence, that he has some nonexistent constitutional right to become a Supreme Court justice, accord no such benefit of the doubt or right of due process to innocent persons, persons not accused of any criminality, who have fairly questioned Kavanaugh’s fitness for high public office.