Hard to calculate such a thing, but it is essentially priceless. He is the presumptive nominee because of the media giving him a massive, massive platform every hour of every day. He doesn't actually know how to get people out to vote, it has been shown several times in several states. The media have handed him this one.
Oh and gullible people (which goes for Clinton voters too). These people are known liars and it is honestly not even remotely difficult to smack some google searches into your keyboard to figure these things out.