They would need to focus on one state in order to do that, and take votes from both sides. I don't see why they would want to do that, though.
The only way a libertarian candidate could keep either candidate from getting to 270 is if they win some electoral votes, but win them from both sides. But the libertarian set is going to be coming exclusively from the Republican side. So basically, no amount of libertarian votes is going to throw this to the House.
Maybe if Jill Stein comes out in favor of banning memes Johnson can get some Bernie Bros.