Green Party Presidential Candidate Jill Stein speaks with media and others gathered at City Hall during the Democratic National Convention in Philadelphia on Monday. Reuters

With Donald Trump officially named the Republican presidential nominee last week and Hillary Clinton poised to become the Democratic candidate Thursday, you may feel like your options for the November general election are locked in.

But you’re wrong. Jill Stein, a 66-year-old physician, is also in the running for the White House.

Stein is on track to become the Green Party’s 2016 nominee for president, just like she was four years ago. And though a third-party candidate has never landed in the Oval Office, Stein is performing well among voters who are dissatisfied with the establishment and faced with choosing between Trump and Clinton. As of Tuesday morning, she was polling at about 3 percent support, according to RealClearPolitics.

"This is how you build political movements — you have to gain trust and you have to work together and that's what you can do in the course of a political campaign. You can test the waters and those waters right now are feeling very warm and welcoming," she told ABC News recently.

Jill Stein | InsideGov

On her website, Stein identifies herself as a mom, doctor, organizer and advocate for environmental health. But these days, she’s also pitching herself as an alternative to Bernie Sanders.

Stein, who has repeatedly classified both Trump and Clinton as dangerous for the United States, is a progressive like the Vermont senator. Since his campaign against Clinton petered out in June, Stein has been courting passionate Sanders fans in speeches and on Twitter. She even made an appearance Monday at the Democratic National Convention in Philadelphia, according to the Huffington Post.

“We are here especially for the Bernie Sanders movement that does not want to go back into that dark night, into the Hillary Clinton campaign, that for so many people represents the opposite of what Bernie was building and what they were building,” Stein told NPR earlier this week. “I think so many people learned that you cannot have a revolutionary campaign inside of a counter-revolutionary party. So we are here as plan B for Bernie to ensure that this fight will go on."

Stein supports tuition-free public education, Medicare for all, living-wage jobs for everyone, clean energy and the end of mass incarceration. She has proposed shuttering the Guantanamo Bay detention center, slashing military spending and improving voter rights, according to her website.

Stein got about 470,000 votes in 2012, which shakes out to about 0.36 percent of the popular vote, according to the Federal Election Commission. So far this year, she’s only on the ballot in 23 states, putting her behind challenger and Libertarian presidential candidate Gary Johnson, who has made it onto all 50 ballots.