Sayoc, who lived in a white truck plastered with pro-Trump and anti-Democrat stickers, was arrested in Florida five days after the first device was discovered in Soros's upstate NY mailbox.
None of the devices exploded before they were recovered by authorities, but tension built as each new device was found in the weeks leading up to the 2018 midterm elections.
Sayoc mailed 16 improvised explosive devices to 13 targets around the United States, including 11 current or former USA government officials, the U.S attorney's statement says.
Cesar Sayoc, 57, shackled at the ankles, briefly sobbed as he entered the plea before a NY federal judge.
Sayoc initially indicated in court that although he packed the devices with fertilizer and powder from fireworks, he intended them only to look like pipe bombs, not to detonate.
The change-of-plea hearing was revealed last week after a phone conference between prosecutors, Sayoc's lawyers and a judge.
JACQUELYN MARTIN APSayoc pleaded guilty to sending explosive devices to critics of US President Donald Trump
He will be sentenced by Manhattan Federal Judge Jed Rakoff on September 12.
He then pleaded guilty to 65 counts of use of a weapon of mass destruction, interstate transportation of an explosive device, conveying a threat through interstate commerce, illegal mailing of an explosive device and carrying an explosive during the commission of a felony.
The 56-year-old has been held without bail in NY since his arrest on 26 October, 2018.
All of the targets had criticized Trump, who had apparently become the focus of Sayoc's intense admiration.
The arrest came just four days after the first of his bombs was discovered at Soros' Westchester County estate, and law-enforcement sources have told The Post that Sayoc had a target list with hundreds of more names on it.
Wasserman Schultz represents the Florida district where Sayoc, a former strip club DJ, lived. Prosecutors said the evidence against Sayoc included DNA that linked him to 10 of the devices and fingerprints on two of them.
Update 10/26/2018: Native American Trump supporter Ceasar Sayoc was named as the pipe bomb mailer suspect that was arrested in Florida today.
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