It's been quite a while since Tom Selleck did anything professionally that caught the public eye, so it's a measure of how well known he was to begin with that he's still such a familiar name and face with the voting public. If you do see a lot of Selleck on your television, chances are you're a viewer of 'Blue Bloods.' Politically speaking, Selleck has a lot in common with the character he portrays in that show.
Selleck describes himself as a libertarian more than someone with strong attachments to any particular party. He's a big believer in the right to bear arms - so much so that he served for a time as a spokesman for the NRA - and once campaigned for John McCain when he stood for office. Interestingly, he felt unable to vote for Clinton or Trump at the last election, feeling neither had views that represented him. Perhaps he'd prefer to stand and represent himself?