opinion who is a celebrity patter? i think celebrity does have currency in kind of affirming your existing beliefs. if you re wavering about a candidate. reporter: a measurable effect, remember 2008, many recognizable faces backed then candidate barack obama. but it was this face who pumped his polls. i m here because of my personal conviction about barack obama. reporter: an endorsement that a northwestern university study found actually translated into votes. the endorsement of oprah winfrey of then senator obama was about a million additional votes in 2008 democratic primary. reporter: let the foning for scores win. trust me, i know a good investment when i see one. reporter: even star athletes weigh in. dennis rodman who last supported