Four years ago, one of China’s largest agricultural importers sent representatives to the Democratic National Convention in Charlotte, N.C., hoping that meetings with elite party officials might yield business opportunities. The company, the Dandong Port Group, was particularly focused on the governors in attendance, according to an interview with Dandong’s general counsel broadcast by Chinese state television.

“If you really want to influence, let’s say, U.S.-China policy,” he said, “it’s almost worth it to have emphasis and influence on the state level.”

The meetings, arranged by a former South Carolina governor, marked a period of expansion in the United States for Dandong and its affiliated companies, involving negotiations with officials in Washington, Arkansas, South Carolina and Virginia. But now, the company’s widening influence is coming under scrutiny by federal prosecutors, who are examining the relationship between Dandong’s wealthy and connected chairman, Wang Wenliang, and Gov. Terry McAuliffe of Virginia, a Democrat who was elected in 2013.

A federal law enforcement official said the inquiry included $120,000 in contributions that a New Jersey construction firm controlled by Mr. Wang made to Mr. McAuliffe’s 2013 campaign and inaugural committee. That official and a second law enforcement official, both of whom asked for anonymity to discuss the matter, said it was a preliminary inquiry of Mr. McAuliffe’s campaign donations, and they provided no detail about the nature and scope of any potential violations being scrutinized.