Top White House aide Mick Mulvaney said Sunday he has "absolutely not" been asked to resign over his public admission that Donald Trump had tied military aid for Ukraine to Kiev's opening a probe into the Democrats. Mulvaney, Trump's acting chief of staff, walked back that admission only hours after making it Thursday, and on Sunday he again revised his explanation of Trump's July 25 phone call with Ukraine President Volodymyr Zelensky, playing down any linkage to a political investigation.