Jill Biden ridicules Nikki Haley's proposal for competency tests

Jill Biden took to CNN on Sunday to criticize Nikki Haley's proposal that political candidates over 75 years old take competency tests in order to run for office.

Arlette Saenz asked, “Nikki Haley, one of the Republican candidates, is calling for mental competency tests for those politicians over the age of 75. What do you think about that?”

Biden answered, "It's ridiculous."

Saenz then asked, “Would your husband ever take one of those?”

Biden answered, “I mean, we haven’t even discussed — we would never even discuss something like that.”

Why would Jill Biden be opposed to a competency test unless she thought her husband had something to hide?