Top Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally 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 Blackburn Marsha BlackburnDemocrats smell blood with new DHS whistleblower complaint Hillicon Valley: Election officials prepare for new Russian interference battle | 'Markeyverse' of online fans helps take down a Kennedy | GOP senators unveil bill to update tech liability protections GOP senators unveil new bill to update tech liability protections 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.