WASHINGTON — For a House freshman and political neophyte, Representative Alexandria Ocasio-Cortez of New York has proved to be remarkably adept at shaping the debate on her Democratic Party’s left flank, boosting the visibility of single-payer health care through her support of “Medicare for all” and elevating climate change with her Green New Deal.

On Wednesday, Ms. Ocasio-Cortez hopes to do for the nation’s poor what she has done with health care and climate politics with the unveiling of an ambitious anti-poverty package that, among other things, would cap annual rent increases, ensure full access to social welfare programs for people with convictions and undocumented immigrants, pressure federal contractors to offer better wages and benefits, and update official poverty measurements by taking into account geographic cost-of-living variations and access to health insurance, child care, and “new necessities” such as internet access.

“I think this really starts to approach, head on, economic injustice in America,” Ms. Ocasio-Cortez said in an interview. “We are at our richest point that we’ve ever been, but we’ve also been our most unequal.”

She added, “it’s something that we have to talk about.”

Since defeating Representative Joe Crowley, a senior member of the Democratic leadership, during the 2018 primaries, Ms. Ocasio-Cortez, 29, has used her social-media following — 4 million followers on Instagram and more than 5 million on Twitter — and strong ties to the party’s progressive wing to shift the party leftward. Her Green New Deal would move the nation’s energy economy rapidly away from fossil fuels, with vague promises of guaranteed job security. Medicare for all would replace all private insurance with one government-run health care system like Britain’s or Canada’s.