I wholeheartedly agree with Theo on this one so will re-post his FB post below. (See the post for his ongoing comments).
“And they cannot influence the Democratic Party in the way Bernie did through his 2016 campaign, because Democratic centrists are more interested in controlling their party than winning elections, as demonstrated by their preference for Hillary in spite of her poor polling among the general electorate. Voting for Stein just demonstrates to the party that left-leaning progressives have no stamina and give up easily.
“The idea that the Green Party needs to run a Presidential candidate to establish itself is as strategically impoverished as it is unimaginative. The Green Party can build itself through a series of campaigns at the local and state level, building up to the House and Senate. If it so chooses it can make itself a serious contender in liberal college towns and urban ghettoes without losing safe Democratic seats. If it does swing some of these elections to Republicans the risk will be distributed, unlike with the Presidency where the consequences could be catastrophic. This was the Green Party strategy in the early nineties when I was a small-time party organizer. The Green Party can also work to oust corrupt and centrist Democrats, much as the Tea Party did from the right.
“The idea that Jill Stein can break the two-party system is simply absurd. Nader was a political genius with as much legislative accomplishment under his belt as many one-term presidents, who might have had a shot at the Presidency if he ran as a Democrat in ’76, and he barely got 2 percent of the vote. Meanwhile, Stein has the resume of a relatively successful small-time non-profit leader, who has been at it for a couple of decades. Imagining her in the Oval Office is as difficult as it is pointless. The current Green Party is simply unprepared consider the Presidency. And this is to say nothing of Trump…”