Speaking to reporters in Washington, DC, what appeared to be hair dye began streaming down Rudy Giuliani's cheeks.
The 76-year-old mopped his brow but failed to realise there were dark brown streaks running from his hairline down to his jaw at the Republican National Committee headquarters.
Giuliani used the news conference to repeat claims that electoral fraud was involved in the process leading to Joe Biden's victory.
Under what were presumably very hot lights, Giuliani wiped his brow again - and his cheeks, too, looking a little sheepish as areporters asked questions.
Amid widespread amusement on Twitter, one user said the Trump aide was "sweating black goo", while another speculated that he had a sponsorship deal with a hair dye manufacturer - which had just been cancelled.
It is the latest in a series of embarrassing events for the former mayor of New York City.
Another news conference was held opposite a crematorium and next to a sex shop.
Film also emerged days before the election of Giuliani inside a hotel room with a 24-year-old actress after she tricked him into going back with her for the new Borat film.