Answer:
Green Party or Democratic Party; it depends.
Explanation:
The Green Party absolutely is "liberal" and are progressives. Jill Stein was a progressive candidate much like Bernard Sanders, and she ran in the 2016 election under the green party ticket.
The Democratic Party has largely fallen from grace. It has become centrist, more right leaning, and corporatist. You can say it's liberal, but that would mostly be factually inaccurate
Third Party doesn't necessarily mean liberal because it is a term for a party that is not Democrat or Republican. The Libertarian Party, Green Party, and Tea Party are all third party organizations
The Republican Party is an obvious one.
