Charles Turner Habermann of Palm Springs appeared in federal court in Seattle to enter the plea Tuesday.
An FBI complaint said Habermann called the Seattle Democrat's office in December and left two messages, each about four minutes long, after seeing him on television. Transcripts say he began each with his name and phone number, and went on to threaten to kill the congressman over his opposition to extending tax cuts for the wealthy.
Habermann reportedly told investigators he has a $3 million trust fund. One of the conditions of his pretrial release is that he not withdraw more than $12,000 per month from the fund.