Nyhan graduated from Mountain View High School in 1996 and later attended Swarthmore College where he received a degree in political science in 2000. He graduated with high honors. In May 2009 Nyhan was awarded a Ph.D. in Political Science from Duke University.
While at Swarthmore, Nyhan and Ben Fritz began the L-Word: Swarthmore's Journal of Progressive Thought. The periodical was launched in May 1997 and their goal was to provide a forum for the diversity of liberal thought which exists at the college. The last issue was in May 1998.
In 2000, Nyhan served as the Deputy Communications Director for the failed "Edward M. Bernstein for US Senate campaign" in Nevada.
From 2001-2003, Nyhan managed new projects and then marketing and fundraising for Benetech, a Silicon Valley technology nonprofit.
From 2001-2004, Nyhan (with Ben Fritz and Bryan Keefer) co-edited Spinsanity, a non-partisan watchdog of political spin that was syndicated in Salon.com in 2002 on-line and the Philadelphia Inquirer in 2004 in print and on the internet. While Spinsanity was active the authors logged over four hundred articles. Spinsanity closed on January 19, 2005.
Nyhan co-authored the non-fiction political book All the President's Spin: George W. Bush, the Media and the Truth in 2004 along with Fritz and Keefer. According to reviewer John Moe the book "detail[s] how Bush and company, more than any administration in history, cherry pick information that they find helpful, regardless of how representative it is of the overall truth, and then package it with a forceful and persistent presentation that eventually takes on the patina of reality."
All the President's Spin reached the New York Times non-fiction paperback bestseller list as #14 in the September 5th edition.
Nyhan has also written for other political and news publications which are on-line such as American Prospect (circa 2002), Time, and others.
In 2011, upon completion of his term as a Robert Wood Johnson Scholar in Health Policy Research, Nyhan will join the faculty of Dartmouth College as an assistant professor of government.
In late 2006 Nyhan was again tapped to write about "media criticism" for the American Prospect. However, after a few essays/posts he came under attack from the editors for unwarranted criticism of liberal pundits. According to Nyhan, "Sam Rosenfeld, the magazine's online editor, asked that I focus my blogging on conservative targets." Rosenfeld denied that this was the case. Nyhan, due to his background writing about such topics, (e.g. Spinsanity) refused and decided to terminate his relationship with the American Prospect (aka TAP).
TAP editor Michael Tomasky said that "[t]he Prospect is hardly averse to criticizing liberal verities" ... but "there were a few posts in succession that struck us as either inaccurate or an effort to draw equivalencies where none existed." Tomasky said that Nyhan had made unfounded allegations for reasons of self-promotion, saying: The Prospect has always opposed a 'pox on both houses' posture, and that's what we came to believe [Nyhan was] doing."