You're confusing libertarians with members of the Libertarian party - they aren't the same thing.
Small "L" libertarians are a huge voting block in both the Republican and Democratic parties, though more so in the Republican party.
With just the social conservative vote (which a decent size still goes to the Dems), the GOP might get about 30% of the general vote - so the question is, do the social conservatives want to be politically relevant or not?
Neither this thread which mentioned about 15%, IIRC, nor this link is talking about the big 'L' Libertarian Party which will rarely be anything other than a spoiler. We're talking about one seventh of the electorate, small 'l' libertarians. Without the dems actively threatening some gun control BS, which they didn't say a peep this time, they can be the swing vote.
Libertarianism in One Country - On the Brink and beyond.
"According to Brink Lindsey, only 13 percent of Americans currently lean libertarian."