Top Donald TrumpDonald John TrumpGOP nearing end game on immigration votes Tech companies scramble as sweeping data rules take effect Comey: Trump's 'Spygate' claims are made up 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 BlackburnKoch-backed group to target some Republicans over spending vote in new ad campaign Trump to hold Nashville rally amid efforts to boost GOP Senate hopeful The Hill's 12:30 Report 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.