Alongside the Trump-Russia Inquiry, a Lesser-Known Look at Egyptian Influence

In the summer of 2017, as the special counsel Robert S. Mueller III was starting his investigation, his agents and prosecutors were chasing potentially explosive allegations about foreign influence over Donald J. Trump and his campaign.

C.I.A. intelligence relayed to the special counsel’s office suggested that senior leaders of a foreign adversary had signed off on secretly funneling millions of dollars — with the help of a Trump campaign adviser acting as “a bag man” — to Mr. Trump in the final days of the 2016 election.

Interviews and other evidence obtained by the special counsel’s office showed that indeed Mr. Trump had lent his campaign a similar amount of money in the final days of the race — and, after beating Hillary Clinton, Mr. Trump immediately struck a far more favorable tone toward the country than his predecessors.

The country in question, however, was not Russia. It was Egypt.

Seven years after Mr. Mueller’s team dug in on those allegations, people familiar with the investigation acknowledged that while much of the country’s attention was focused on ties between Mr. Trump’s campaign and Russia, the most concrete lead Mr. Mueller’s team initially had about potential foreign influence over Mr. Trump involved Egypt. The people familiar with the inquiry discussed details of it on the condition of anonymity.

While Mr. Mueller has often been criticized for not moving aggressively enough to investigate Mr. Trump’s personal and financial ties to Russia, his team took invasive steps to try to understand whether Mr. Trump or his campaign had received financial backing from Cairo.

Mr. Trump’s foreign business ties and efforts by foreign interests and government to influence him have come under scrutiny again as he seeks to return to the White House. The little-known investigation into possible Egyptian influence shows both the intensity of past efforts to explore the issue and how they have fueled Mr. Trump’s long-running assertions that he has been subject to a “witch hunt.”