One possible explanation for Kasowitz’s decision not to pursue a clearance: He might have trouble getting one.

In recent weeks, ProPublica spoke with more than two dozen current and former employees of Kasowitz’s firm, Kasowitz Benson Torres LLP, as well as his friends and acquaintances. Past and present employees of the firm said in interviews that Kasowitz has struggled intermittently with alcohol abuse, leading to a stint in rehab in the winter of 2014-15.

Several people told ProPublica that Kasowitz has been drinking in recent months. (The vast majority of those who spoke to ProPublica for this article declined to be quoted by name, citing Kasowitz’s penchant for threatening lawsuits.)