(Bloomberg) —Donald Trump has discussed in recent days the possibility of selecting former House Speaker Newt Gingrich as his vice presidential running mate, according to multiple people familiar with the discussions.

Trump, the presumptive Republican presidential nominee, has been asking confidants for input on Gingrich as a potential pick, including during conversations Wednesday at Trump Tower in New York, according to a person familiar with the discussions.

The presumptive Republican nominee told the Associated Press that he has narrowed his vice presidential list to “five or six” candidates, and has named Corey Lewandowski to head up the vetting process “with a group” of staffers.

On Fox News Tuesday night, Trump said he was also considering former Arizona Governor Jan Brewer and Oklahoma Governor Mary Fallin. Others said to be under consideration include Iowa Senator Joni Ernst, Florida Senator Marco Rubio and New Jersey Governor Chris Christie, all Republicans.

Former Republican presidential candidate Ben Carson, who this week concluded his role in helping compile the list of possible running mates for Trump, also recommended Gingrich, according to a person with direct knowledge of the list.

There’s a strong rationale for Gingrich, said Rick Tyler, who was an aide to the lawmaker for 12 years in Congress and during Gingrich’s 2012 presidential bid. He has substantive policy-driven views and knows the world, Tyler said.

Tyler said he’s “confident” Gingrich is being considered, and could see him acting as a senior adviser in a manner similar to former Vice President Dick Cheney.

Gingrich didn’t respond to two calls for comment.

There are several approaches that can be used to selecting a vice president: pick someone who compensates for a candidate’s weaknesses or echos a strength. Gingrich might do both. Gingrich could help activate the Republican base, but likely would do little to gain support from minorities or independent voters.

Liaison to Washington Gingrich has been a behind-the-scenes cheerleader for Trump in recent weeks and has sought to serve as a liaison between Trump and Washington Republicans. Earlier this week, he pushed back against speculation that another Republican should run as a third-party candidate. “You can be for the Hillary Clinton team or you can be for Donald Trump to defeat Hillary Clinton. There’s no honest, realistic third choice,” Gingrich told TIME magazine.

Gingrich is often credited with infusing his party with new ideas, and his presence may comfort conservatives who say Trump’s campaign has been light on policy proposals.

The former U.S. House speaker is both bomb-throwing outsider who built a career running against the establishment, and a skilled Washington insider who knows about government.

A historian by training, and holds a doctorate in European history and he’s known for his intellectual curiosity. He also knows how to play political hardball, and has gone toe-to-toe with the Clintons, having helped lead the calls for former President Bill Clinton’s impeachment over his marital infidelity with Monica Lewinsky. Gingrich later admitted to having his own extramarital affair.

While in Congress, he immersed himself in policy, military affairs and security intelligence, and has a resume of accomplishments, including an overhaul of welfare.

“Trump needs a VP who will sing from the same hymn book he does on the campaign trail, pacify conservatives and can pull the right levers of power in D.C. to get things done once in office,” said Ford O’Connell, former campaign adviser to 2008 Republican nominee John McCain. “Gingrich, without question, fits that bill.”

Gingrich’s presidential ambitions ended after his own unsuccessful 2012 White House run. During that campaign, he sought to portray himself as a more conservative alternative to eventual Republican presidential nominee Mitt Romney, but was ridiculed by Romney for floating the idea of building a permanent outpost on the moon for “science, tourism, and manufacturing” by the year 2020.