Jurors began to deliberate on Tuesday over the fate of Ryan W. Routh, the man accused of plotting to kill President Trump at one of his Florida golf courses last year, following a fast-moving trial in which Mr. Routh chose to defend himself without a lawyer.

“Make no mistake: The defendant was going to kill Donald Trump,” Christopher B. Browne, one of the federal prosecutors, said during his closing argument. “The defendant was just one bullet away.”

He urged jurors to find Mr. Routh guilty of attempted assassination, a charge that carries a maximum penalty of life in prison, as well as of assaulting a federal officer and several firearm violations.

Mr. Browne said the evidence showed that Mr. Routh, 59, planned the attack for months and tracked Mr. Trump for weeks before hiding just outside the fence of the Trump International Golf Club West Palm Beach on Sept. 15, 2024, with a semiautomatic rifle in hand, while Mr. Trump played golf.

Prosecutors said that Mr. Routh pointed the rifle, whose serial number was scratched off, at a Secret Service agent who spotted him in the shrubbery by the fence. The agent fired at him, and Mr. Routh fled without firing any shots of his own, they said. The police stopped Mr. Routh about 45 minutes later, driving north on Interstate 95.

In his closing argument, Mr. Routh spoke about himself in the third person and said that prosecutors had not proven “any intent” to kill.