The Justice Department filed a notice Friday to re-try Democratic New Jersey Sen. Bob Menendez on bribery and corruption charges.
An 11-week trial last fall resulted in a hung jury.
Menendez and co-defendant Dr. Salomon Melgen pleaded not guilty to all charges.
In a statement, the Justice Department requested the court set "the earliest possible date" for the new trial.
"Sen. Menendez and Dr. Melgen were indicted in the District of New Jersey on charges that included conspiracy, bribery, and honest services fraud," the department said. "The decision to retry this case was made based on the facts and the law, following a careful review."
The retrial could become a major headache for Democrats in the 2018 midterms.
He's running for re-election this year despite his legal trouble and already has become a punching bag for national Republicans, who have sought to tie Menendez to other Democrats on the ballot this year.
Three Republicans are running to oppose Menendez, including Jeff Bell, the party's nominee against Democrat Cory Booker in 2014, and Army veteran Rich Pezzullo.
Republicans have had recent success in the state. Though former GOP Gov. Chris Christie exited with record low approval ratings, he was elected twice. In last year's gubernatorial election, Democrat Phil Murphy won by 13 percentage points -- a high mark that Menendez is unlikely to top.
Democrats who closely watched Menendez's first trial as they weighed bids for his office, including former Sen. Bob Torricelli, ultimately decided against challenging him in the party's primary.
"To those who were digging my political grave so that they could jump into my seat, I know who you are, and I won't forget you," Menendez said after the hung jury in November.
Attorneys for Menendez and Melgen did not immediately comment on the retrial decision.
November's mistrial was a serious blow to the Justice Department, which has investigated Menendez for nearly five years.
At the time, the senator said he felt vindicated.
"I want to thank the jury, 12 New Jerseyans who saw through the government's false claims and used their Jersey common sense to reject it," he told reporters outside the courthouse, before blasting the Justice Department.
"The way this case started was wrong, the way it was investigated was wrong, the way it was prosecuted was wrong, and the way it was tried was wrong as well," he said. "Certain elements of the FBI and of our state cannot understand or, even worse, accept that the Latino kid from Union City and Hudson County can grow up and be a US senator and be honest."
Shortly after the mistrial, Senate Majority Leader McConnell, R-Kentucky, called for a Senate Ethics Committee investigation.
Menendez faced charges of conspiracy, bribery, and honest services fraud related to allegedly abusing the power of his office that could carry decades in prison. Prosecutors say the senator accepted more than $600,000 in political contributions, a luxurious hotel suite at the Park Hyatt in Paris, and free rides on a private jet from Melgen, a wealthy ophthalmologist, in exchange for political favors.
Defense lawyers argued that Menendez and Melgen were longtime friends with no corrupt intent to commit a federal crime.
Prosecutors relied mostly on circumstantial evidence to prove their case -- spending the opening weeks of trial painting a jet-setting lifestyle of the rich and powerful before ultimately turning to the "official acts" they argued Menendez did to help his friend.
They accused Menendez of pushing officials to help resolve an $8.9 million Medicare billing dispute in Melgen's favor, while the defense team claimed at trial that the senator was focused on the fact that the billing policies at issue were conflicting and the drug companies were enjoying a windfall.
Similarly, when several State Department witnesses testified that Menendez had threatened to hold a congressional hearing if they did not intervene in a contract dispute between Melgen and the Dominican Republic over cargo screening at the nation's ports, the defense said that the senator was troubled by port security more generally.
After the trial ended, one juror, Ed Norris, told reporters the jury was split 10-2 on all counts in favor of acquittal.