Jeffrey Sonnenfeld, an associate dean at the Yale School of Management and an expert on corporate leadership, has become a surprising bit player in the 2016 presidential campaign.

At last week’s CNN Republican presidential debate, Donald Trump cited Mr. Sonnenfeld as saying Carly Fiorina had “one of the worst tenures for a C.E.O. that he has ever seen.” Mrs. Fiorina retorted that Mr. Sonnenfeld was “a well-known Clintonite and honestly had it out for me from the moment that I arrived at Hewlett-Packard.”

Mr. Sonnenfeld, who is a contributor to CNBC and a frequent commentator on corporate performance, does have a long history of colorful criticism of Mrs. Fiorina. In 2008, when she was campaigning for John McCain, he told this newspaper “you couldn’t pick a worse, non-imprisoned C.E.O. to be your standard-bearer.” His criticism has been similar to those offered by many business analysts and journalists: that Mrs. Fiorina increased the overall size of H.P. by expanding in unprofitable businesses, which caused profits to shrink and shareholder value to decline.

This week, he updated that critique with an article for Politico Magazine titled “Why I Still Think Fiorina Was a Terrible C.E.O.” In addition to arguing that H.P.’s financial performance lagged its peers under Mrs. Fiorina, and insisting that he was not a “Clintonite,” he complained that she “is intolerant of dissent and resorts to personal attacks.”