I understand protest voting; I'd have voted for Gary Johnson in 2012 against Romney. I would have voted for Ron Paul if he were the nominee. Gary Johnson, being the closest candidate to Ron Paul, would have been a sensible choice. So would have been Virgil Goode to a lesser extent.
Sasse, a supporter of war hawk/"Reagan Conservative" Marco Rubio has nothing in common with Gary Johnson or the Libertarian Party. In fact, many Sasse fanboys like Erik Erikson endorsed his socially conservative rival Austen Peterson. They failed to hijack the LP (ironically forming an unholy alliance with the party radicals) and are tentatively behind Johnson not out of any remote ideological similarities (ironic because they complain Trump has no core ideology) but rather out of a simple desire to spoil the election. If they wanted a third party alternative, then David French should have run.
Had Marco Rubio been the nominee, Sasse would be bitching up a storm. They want their guy over the will of the rest of the party. People like me who are at least intellectually honest in their voting who backed Johnson in '12? We were RINOs then. Back the party this year? We're stupid. Well, this stupid RINO has done more for this party in the last week then Vosem and company have ever done. I'd be willing to venture the same about the nakedly ambitious Ben Sasse.
Sanchez, did Sasse ever endorse Rubio? I don't recall if he did, I know he ran as a Ted Cruz type of conservative for Senate and that's what I remember him as. Maybe he's a hawk, but I don't think I would put him in the same camp as the neoconservatives or establishmentarians.
He almost certainly will not actually vote for Johnson. It looks like he's looking for attention and wants to build up some kind of reputation as a conservative maverick and then run for president down the line.