[7][8][9] He has served as a political operative for the Democratic Party and as head of community and content for Sidewire from January 2016 to the service's closure in June 2017.

[9] In the mid-1990s, Allen attended St. Mary's College of Maryland, where he played as a pitcher on the baseball team and worked as a sports reporter for the university's Point News.

[16] After graduating from college, Allen briefly worked at the local Prince William Journal before joining Congressional Quarterly in 2000 as a copy editor.

[4] After working for Maryland Senator Paul Sarbanes, Allen was quickly hired by Representative Debbie Wasserman Schultz as executive director of Democrats Win Seats, a political action committee.

[4][16]In 2012, Allen partnered with journalist Amie Parnes of The Hill to write a book on then U.S. Secretary of State Hillary Clinton that focused on her tenure and political future.

Though the book was a New York Times Best Seller, it was negatively received by critics, who felt the authors had portrayed Clinton too sympathetically.

"[26] A widely publicized finding from Allen and Parnes' reporting was an enemies list compiled by Clinton's campaign staff in 2008.

[30] Initially hired to cover the White House and Hillary Clinton's anticipated 2016 presidential campaign, he was eventually promoted to Washington bureau chief.

[31] Allen served as chief political correspondent for Vox until October 2015, leaving to focus on a follow-up book on Hillary Clinton.

[32] In April 2014, Crown Publishing Group officially announced that Allen and Parnes would collaborate on a book centered on Clinton's anticipated 2016 presidential campaign.

In a 2017 interview with Charlie Rose, Allen stated that: ...we had this discussion before the election as we were talking to our editor about the fact that we had identified a lot of problems even though it looked like she was going to win.

[35] The book received positive reviews from critics such as Michiko Kakutani of The New York Times and David Shribman of The Globe and Mail.

[37] Christa Reynolds, the Clinton campaign's deputy communications director, refuted the book's claims in a blog post.

After leaving Vox in October 2015, Allen served as head of community content for Sidewire, a political news analysis platform.

According to Allen, he saw potential in Sidewire following a post by Senator Lindsey Graham, who used the platform to discuss the presidential debate he had been excluded from.

Carlos Lozada of The Washington Post wrote that the book "provides useful detail to understand Biden's victory, even if the framing is not particularly novel.

"[40] According to Jennifer Szalai of The New York Times, "the granular politicking ably recounted in Lucky is a necessity—but what becomes unintentionally clear is how wasteful so much of it is.

[4] Alongside his own time as a political operative, Allen's wife Stephanie served as communications director for Democratic senators Mary Landrieu and Kay Hagan.