Rand Paul in November, abandoning him with six broken ribs, pleaded guilty Friday.
The retired doctor, who has lived next to Paul in Bowling Green, Ky. for over 17 years, is accused of attacking the senator in November.
Baker said Friday that the attack was a "complete lapse in judgment" by Boucher.
The two had an ongoing dispute over yard maintenance for a few months.
The episode had been "profoundly embarrassing" for Boucher, his lawyer, Matt Baker, said.
Boucher's father died sometime after the incident with Paul, Baker said, adding to what has been a hard few months for Boucher. "He still feels as though he has the weight of the world on his shoulders".
Boucher left the federal court building without speaking to reporters.
Federal prosecutors recommended a sentence of 21-months. The charge carries maximum penalties of 10 years in prison and a $250,000 fine. Baker says he'll argue for probation.
According to Associated Press, Boucher has agreed to pay restitution to Paul, but the amount will be confirmed during the sentencing later this year. A friend of Paul's said the senator had gotten off his riding mower to remove a limb when he was tackled from behind.
He also characterized the attack as a dispute that boiled over that had nothing to do with politics.
Boucher has been released on a $25,000 bond has been ordered to abstain from any contact with the senator or the Paul family.