After Needham graduated from Williams in 2004, he received a job at the Heritage Foundation, a conservative think tank, with the help of fellow Williams graduate and California politician Bill Simon.[3] Described as "ambitious and hard-working," within six months he was promoted to be chief of staff to Heritage Foundation president Edwin Feulner.[3] After three years at the Foundation, he joined Rudy Giuliani's presidential campaign in 2007, where he worked until 2008.[2]
Needham co-wrote the business plan for Heritage Action, the Heritage Foundation's sister organization, while attending Stanford.[4] According to The Washington Post, he had been enlisted by Feulner "to launch a group that would hold lawmakers accountable for their votes."[2] In April 2010, he and Feulner co-wrote an op-ed in the Wall Street Journal announcing the founding of Heritage Action, titling it "New Fangs for the Conservative Beast," and describing the new organization as the "fangs" for the Heritage Foundation's "beast."[2] Needham was named the group's first chief executive officer (CEO).[3]
The New York Times described Needham as "a leading practitioner of the uncompromising, scorched-earth style of political combat that was a trademark of Tea Party-inspired politicians and activists."[5] He led Heritage Action as it became one of the most influential conservative lobbying groups.[2] He was described as a major opponent of "the establishment" and The Washington Post noted that he "stok[ed] fear in Republicans long before Donald Trump."[2] He led the group's advocacy to stop the Affordable Care Act (ACA) and led the group as they played an instrumental role in the 2013 United States federal government shutdown, with the Wall Street Journal dubbing Needham "the strategist behind the shutdown."[2][3][6]
After eight years as CEO of Heritage Action, Needham left the group in 2018 to become the chief of staff for Florida U.S. Senator Marco Rubio.[5] He served five years as Rubio's chief of staff before departing in June 2023 to found America 2100, a think tank which Needham then became president of.[7][8] He later also joined American Compass, a think tank created by Oren Cass, as chairman in July 2024.[9]