According to two different reports, after making the decision last night Trump was on the phone until early in the morning asking aides if he could change his mind.
Sources tell me @realDonaldTrump was on phone till midnight making calls, asking if he could change course on VP pick— Kelly O'Donnell (@KellyO) July 15, 2016
Trump's senior communications advisor, however, denies this:
This is completely false. Zero truth to it. https://t.co/xC8QAV17W3— Jason Miller (@JasonMillerinDC) July 15, 2016