Representative Alexandria Ocasio-Cortez, the popular freshman Democrat from New York who is trying to use her star power to move the Democratic Party to the left, will headline a rally next week in Washington in favor of the Green New Deal, as she seeks to shore up support for the expansive climate legislation that has been met with skepticism by members of both parties.

Ms. Ocasio-Cortez, a co-sponsor of the Green New Deal, has long aligned herself with Sunrise Movement, the collection of young, hard-charging activists who are pressuring Democrats nationwide to take bolder actions to address climate change after years of what they see as an inadequate response.

The May 13 rally at Howard University, the final stop on the group’s nationwide “Green New Deal Tour,” will make the case for the bill in the backyard of Capitol Hill, where party establishment figures such as Nancy Pelosi, the House speaker, and Chuck Schumer, the Senate minority leader, have been more wary of their party’s progressive flank than many in their rank-and-file.

“From fire-scarred California to areas of the plains devastated by flooding, people are hungry for a big vision to transform our economy in line with science and justice demands,” said Varshini Prakash, a co-founder of Sunrise Movement. “I’m thrilled to be joining Representative Ocasio-Cortez to close out the tour and lay out what’s next in the Green New Deal campaign.”