- Walker previously spoke at the Republican National Convention
- The vice presidential debate will take place at Longwood University on October 4
They've only had one session so far, the source added.
Meanwhile, lawyer and agent Bob Barnett is playing Pence in debate prep sessions with Kaine, a person close to the process told CNN Saturday. The move was first reported
Barnett is also helping with Democrat Hillary Clinton's debate prep, but is more directly focused on Kaine's, the source added.
Pence, the Indiana governor, will face off with Kaine, a senator from Virginia, on October 4 at Longwood University in Farmville, Virginia. They'll be the only two candidates onstage; vice presidential nominees Bill Weld of the Libertarian Party and Ajamu Baraka of the Green Party failed to quality, the Commission on Presidential Debates announced Friday.
Walker, who mounted his own 2016 presidential campaign but dropped out before the first primary votes were cast, was one of the few nationally known establishment Republicans to speak at the Republican National Convention in support of Donald Trump.
Much has been made of the presidential candidates' conflicting debate styles. Clinton is intensely studying Trump's policy positions, personality and politics by watching highlight reels of Republican primary debates and taking notes on his attack methods.
Trump is preparing by vocally mulling over policies and strategies in ongoing conversations with top campaign advisers as well as with informal aides, including former Fox News chairman and CEO Roger Ailes and former New York City Mayor Rudy Giuliani.
A campaign official told CNN that Trump is doing debate prep on Sunday. It was not immediately clear where the prep would be taking place or who would be involved.