A native of Dawson Springs, Kentucky, Jennings received his bachelor's degree in political science from the University of Louisville in 2000 where he was a McConnell Scholar.

While at WHAS, Jennings won an award from the Associated Press for a series on the plight of the homeless living in downtown Louisville.

He served as associate director in the Office of Political Affairs at the White House before being named special assistant to the president in October 2005.

He has made hundreds of appearances on the network on AC360 with Anderson Cooper, The Lead with Jake Tapper, CNN Tonight with Don Lemon, and other programs.

After losing New Mexico to Al Gore in 2000 by just 366 votes, President Bush's reelection campaign dispatched Jennings to manage its operations there.

In 2019, Jennings made television and radio ads for Attorney General Daniel Cameron,[17] the first stand-alone African-American candidate to win statewide office in Kentucky.

"[19] On April 23, 2007, the U.S. Office of Special Counsel (OSC) announced it was investigating the January video conference, to look at whether the political dealings of the White House had violated the Hatch Act.

He invoked executive privilege and refused to answer most questions, claiming the president George W. Bush had ordered his non-compliance.

"[24] E-mails published subsequently confirmed that Jennings was directly involved in the controversial firing of New Mexico US Attorney David Iglesias, Jennings writing in one e-mail to a White House staffer, "Iglesias has done nothing," and to another, "We are getting killed out there," adding that the White House "move forward with getting rid of the NM USATTY.".

"[19] Jennings ran a Super PAC known as Kentuckians for Strong Leadership that supported the re-election of Mitch McConnell during the 2014 U.S. Senate election in Kentucky.

In July 2014, Jennings told radio station WFPL "I think the party is coming together just fine and I don't detect any problems for McConnell on GOP unity.

"[28] In 2016, Jennings' Super PAC, Kentuckians for Strong Leadership (KSL), sought to help Republicans gain control of the Kentucky House of Representatives.

[34] In June 2017, Jennings joined CNN as a political contributor, along with former Clinton campaign manager Robby Mook, former John Kasich chief strategist John Weaver, former Virginia attorney general Ken Cuccinelli, former Obama national security aide Shawn Turner and Yale Law School associate dean and former FBI special agent Asha Rangappa.

He taught a series of seminars on tribalism in American politics,[36] and attracted such guest lecturers to his class as Senate Majority Leader Mitch McConnell[37] and former White House Chief of Staff and RNC Chairman Reince Priebus.