He was the chief media advisor to five successful presidential primary and general election campaigns, and is a co-founder of No Labels, an organization dedicated to bipartisanship and political problem solving.

McKinnon is the co-creator, co-executive producer, and co-host of Showtime's The Circus: Inside the Greatest Political Show on Earth and consulted on the HBO series The Newsroom and Netflix's House of Cards.

[3][4] McKinnon has worked for many causes, companies and candidates, including former President George W. Bush, Senator John McCain, Texas Governor Ann Richards, Congressman Charlie Wilson, and musician and philanthropist Bono.

[12][15] While working for the newspaper, he was jailed briefly on a First Amendment issue after refusing to provide to police unpublished photographs of an Iranian student protest.

[11] During this period he also investigated Child prostitution rings he alleged operated within Texas, discussing his findings on the public access TV show, Alternative Views.

[12] He spent the next several years working on many Texas Democratic winning campaigns,[21] including those of Governor Ann Richards (1990),[14] former Houston Mayor Bob Lanier (2001),[19] and the Congressman Charlie Wilson.

In his Texas Monthly article entitled "The Spin Doctor Is Out", McKinnon wrote that he "won't miss desperate candidates, manic campaign managers and last-minute attack and response ads".

"[21] During a Frontline interview describing the former president's ascendance into the national political arena, McKinnon said, "Governor Bush was doing some things that really got my attention.

[12][26] He worked on Bush's first presidential campaign as the chief media advisor, directing the advertising effort in 2000, a role he would reprise in the 2004 elections.

[27] McKinnon began serving as the principal media advisor for Senator McCain's presidential bid for the Republican primaries in January, 2007, but decided to leave the campaign on May 21, 2008.

[31] According to Rory O'Connor from The Huffington Post, McKinnon felt that he was keeping true to his pledge in not attacking Obama by only "acting as a facilitator to help with Cindy's speech.

According to the duo, "(Rick) Davis had pleaded with Mark McKinnon, who had decided to sit out the general election because he wanted no part of flaying Obama, to ride to their rescue; he agreed, but just for that one night.

He has served on the boards of non-profit organizations countering the influence of money in politics, including CounterPAC, Mayday PAC, and Take Back Our Republic.

[50][51][52] McKinnon helped lead the effort to overturn the United States' same-sex marriage ban by serving as co-chair of Southerners for the Freedom to Marry, alongside Julian Castro.

[54][55][56] He has a tattoo on his right arm of the number "40," in remembrance of the NFL football player and US soldier, Pat Tillman, who was killed by friendly fire in Afghanistan.