Most polls ask respondents about Trump vs. Clinton, and then ask the same question again "with Libertarian Gary Johnson added to the mix" like it's an afterthought.

But if you want to be as close to accurate as possible, Johnson should be included in all polls given he'll be on the ballot in all 50 states. There will be no case where your choice is either Trump or Clinton only.

And if Jill Stein gets on most or all ballots, she should be included as well. Where Johnson is pulling equally from R's and D's, Stein's presence could be damaging to Hillary as she'll pull almost exclusively from D's and Bernouts, even if it's just a few percentage points.