Someone did take Madonna up on her offer:
https://www.nydailynews.com/news/election/madonna-withdraws-oral-sex-promise-hillary-voters-article-1.2864602
With typical results, it could be added.
“A bribe need not take the form of money; it may include items of pecuniary value given in exchange for a vote,” said the legal website USLegal.com.“
Heh heh heh....they said pecuniary.