Top Donald TrumpDonald John TrumpPaul Ryan defends Navy admiral after Trump's criticism Trump discussing visit overseas to troops following criticism: report Retired Army General: Trump is ‘acting like an 8th grader’ in attacking ex-Navy SEAL who led bin Laden operation MORE aide Corey Lewandowski said Sunday the presumptive Republican presidential nominee's campaign is closing in on a running mate.

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"I can say that the list is very small, and we have a very good understanding of who those individuals will be and the decision will be made by Mr. Trump," Lewandowski said on "Fox News Sunday."

Lewandowski is in charge of the team that will vet potential vice presidential candidates.

Several prominent Republican names have been floated, including New Jersey Gov. Chris Christie, former Speaker Newt Gingrich, Rep. Marsha BlackburnMarsha BlackburnTennessee New Members 2019 McConnell reelected as leader, Thune promoted to whip Rick Scott appears with GOP senators, ignores voter fraud question as recount continues MORE (Tenn.) and South Carolina Gov. Nikki Haley.

Trump said earlier this month he would stick with tradition and name his running mate at the Republican National Convention in July.