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Beto O'Rourke, the Democrat challenging Sen. Ted Cruz for his U.S. Senate seat, received threats earlier this year from the suspected pipe bomber in Florida.

A spokesman for O'Rourke, a Democrat in a heated Senate race against Cruz, says Cesar Sayoc used Facebook to send threatening messages in April. O'Rourke did not receive a suspicious package in the mail, said the spokesman, Chris Evans.

Sayoc, 56, was arrested and charged Friday in connection to a series of pipe bombs that were mailed to fervent critics of President Donald Trump, including former president Barack Obama and former Secretary of State Hillary Clinton. Law enforcement sources told NBC News that Sayoc had a list of 100 potential targets and did research on political figures, journalists and entertainers.

Sayoc was charged with five federal counts: interstate transport of explosives, mailing of explosives, threats against former presidents, making threatening interstate communications and assault of current or former officials. He faces up to 48 years in prison if convicted on all counts.

O'Rourke has picked up steam in recent months and given Cruz, an incumbent Republican senator, a tough re-election battle. O'Rourke raised a record-breaking $38.1 million in the last fundraising quarter, with more than 800,000 individuals contributing to his campaign.

Evans said the Facebook messages were reported to U.S. Capitol police at the time. He said FBI agents and dogs have also been at their campaign office in El Paso.