Story highlights Pence compared Trump to Ronald Reagan

Pence is on the short list of possible Trump running mates

Indianapolis (CNN) As anticipation builds for Donald Trump to name his vice presidential pick, two hopefuls -- Indiana Gov. Mike Pence and former House Speaker Newt Gingrich -- appear to be the front-runners, according to a person familiar with the deliberations.

Also still in the mix: New Jersey Gov. Chris Christie. Trump will likely make the announcement on Friday, the source said.

Pence introduced Trump at a rally Tuesday in Indiana that served as an audition of sorts as the presumptive Republican nominee closes in on a decision. The Indiana governor happily played the role of attack dog by slamming Hillary Clinton and saying she "must never become president of the United States."

Pence and Trump had a private, one-on-one conversation at the fundraiser, according to a source who was there.

"You're gonna call him ... and you're gonna say governor -- or vice president -- we're winning too much!" Trump said of Pence at the rally.

Read More