This question was partially addressed in Winter is Trumping:
Making Westeros Great Again!
There is no easy answer to this, you can see elements of Donald Trump's personality in a variety of Game of Thrones characters.
.@jpodhoretz @iowahawkblog I wouldn't be surprised if a DNA test showed he was related to Walder Frey @JonahNRO pic.twitter.com/IWadh6nEaC— Evi L. Bloggerlady (@MsEBL) May 3, 2016
Trump does have a Tywin Lannister thing going...
Trump also a bit like Alliser Thorne
But there is an obvious choice:
I am a big fan of Diana Riggs' character on GoT but she is not Hillary (the character Olenna Tyrell is also way smarter than Hillary)