FORT LAUDERDALE, Fla. — A convicted drug trafficker is accused of stalking nearly a dozen judges in one Florida county by making obscene phone calls and sending letters in which he threatened to be their ‘‘biggest nightmare.’’

Todd Watson, 53, was arrested Tuesday in Fort Lauderdale on 15 misdemeanor charges, including five counts of stalking judges and 10 counts of making obscene calls, news outlets reported.

Investigators said Watson was sentenced in Broward Circuit Court in 2011 to six years in prison. Watson began stalking and harassing judges after his release in March, according to a 39-page complaint.