Trump's VP search accelerates

Donald Trump’s search for a running mate is intensifying, as the former president awaits sentencing on felony charges and prepares for next month’s Republican National Convention.

Vice presidential contenders recently received vetting materials, five sources familiar with the process told NBC News.

Trump’s search, according to one source, is heavily concentrated on four top prospects: North Dakota Gov. Doug Burgum and Sens. Marco Rubio of Florida, Tim Scott of South Carolina and JD Vance of Ohio. Another source described a three-way competition involving Burgum, Rubio and Vance.

It’s unclear, though, who all has been asked to provide vetting details that could rule them in or out. Burgum, who has been spending more time with Trump in recent weeks, is among those who have received a request, said one source familiar with the ask. Advisers to Burgum and other would-be running mates declined or did not respond to requests for comment this week.

Sources plugged into conversations about the search cautioned that Trump is working from a fluid shortlist that at times includes more than a half-dozen names. Additions, subtractions and the emergence of dark-horse candidates remain possible.

Others who have been mentioned as prospective running mates include South Dakota Gov. Kristi Noem, Reps. Elise Stefanik of New York and Byron Donalds of Florida and Ben Carson, who served as the Trump administration’s Housing and Urban Development secretary.

"Anyone claiming to know who or when President Trump will choose his VP is lying, unless the person is named Donald J. Trump," Trump campaign senior adviser Brian Hughes said.

Trump and his advisers have kept a close hold on the search, which until recently had been relatively quiet, as