[9] He began his career as a speechwriter for the U.S. Committee for UNICEF, writing for Audrey Hepburn, among others, and his international coverage includes reporting from Liberia and Iraq.

Bai's first book, The Argument, published in August 2007, is an account of the "new progressive movement" in America and the people who built it.

Bai discussed this aspect of the book on The Daily Show with Jon Stewart[13] and on NPR's Fresh Air,[14] among other venues.

Reviewing All the Truth Is Out in The New York Times, Jack Shafer called it "a mini classic of political journalism".

[12] The New Yorker's media critic, Ken Auletta, wrote, "Bai's superb book provokes many questions, and I gulped it down in a single sitting".

[15] Bai co-wrote the screenplay for The Front Runner, the cinematic version of All the Truth Is Out, along with the screenwriter Jay Carson and the film's director Jason Reitman.

[18] Bai has also written for television, and in 2014, he played himself in two episodes of the Netflix series House of Cards, as part of a season-long storyline involving a magazine story he was writing in the show.