Campaign buttons for Libertarian presidential candidate Gary Johnson and vice-presidential candidate Bill Weld at the National Libertarian Party Convention on May 27 in Orlando. (John Raoux/AP)

Almost two months ago, I documented a fascinating prediction: The forecasters at Good Judgment were increasingly confident that a third-party presidential candidate could actually win at least 5 percent of the vote — a rate of success that third parties or independent candidates rarely reach in presidential elections.

Now, that forecast has become even more confident:

There is now slightly better than a 50-50 chance that a third party could get at least 5 percent of the popular vote. That’s striking.

It’s all the more striking because the polling numbers for perhaps the most prominent third-party candidate — the Libertarian Party’s Gary Johnson — haven’t really changed. Currently Johnson sits at 8 to 9 percent in polls that include him as an option. His campaign has also attracted support from some Republican leaders: He has been endorsed by one current and two former Republican members of Congress.

Given that third-party candidates typically see their poll numbers decline, this forecast suggests that Johnson’s decline may be small.

Johnson’s possible success doesn’t appear likely to affect whether Clinton or Trump wins the election, but certainly it would be a noteworthy achievement in a political system that otherwise makes it very hard for third parties.