It's just rumors:

A new book about tea party darling Sarah Palin has a salacious revelation about her sex life involving a well-known Miami sports star.
According to The National Enquirer, which obtained an advance copy of a book about Palin by investigative writer Joe McGinniss — Palin and former Miami Heat player Glen Rice had a one-night tryst back in 1987.
At the time, the former Alaska governor, now 47, was single, just out of college and working as a sports reporter at Anchorage TV station KTUU.