(Reuters) - Republican U.S. Senator Lindsay Graham testified on Thursday as a character witness on behalf of Democratic colleague Bob Menendez, who is on trial on federal corruption charges in Newark, New Jersey.

File photo: Chairman Sen. Lindsay Graham (R-SC) reads a letter from the FBI at a Senate Judiciary Subcommittee on Crime and Terrorism hearing about Russian election interference on Capitol Hill in Washington, D.C., U.S. March 15, 2017. REUTERS/Aaron P. Bernstein

Graham testified for only six minutes, telling jurors he knows the New Jersey senator to be a “very honest, trustworthy man,” according to Twitter posts from a reporter from the Star-Ledger newspaper who was in the courtroom.

Democrat Cory Booker, who is New Jersey’s junior senator, also is expected to testify as a character witness. Booker, the former mayor of Newark, has previously attended the trial in support of Menendez.

A statement from Graham’s office said his testimony would be about his service with Menendez and not about the charges against him. Graham, who represents South Carolina, traveled at his own expense, the statement said.

As Menendez entered the courthouse on Thursday, he told reporters he was “honored” that Graham and Booker would testify.

Menendez, 63, is accused of taking bribes from a wealthy benefactor, Florida ophthalmologist Salomon Melgen, in exchange for using his office to help Melgen.

Menendez and Melgen have denied wrongdoing, saying their relationship was simply a close friendship.

Prosecutors say Menendez intervened on Melgen’s behalf with Medicare officials after the agency concluded the doctor had overbilled it by millions of dollars. Melgen was convicted separately earlier this year of a massive Medicare fraud.

Menendez also is accused of pressuring federal officials to secure visas for Melgen’s girlfriends and resolving a port dispute involving one of Melgen’s businesses.

In exchange for Menendez’s aid, Melgen gave the senator private flights, luxury vacations and hundreds of thousands of dollars in campaign money, prosecutors said.

The case has been closely watched in Washington, where Republicans hold a 52-48 edge in the Senate. If Menendez is convicted and either resigns or is expelled before Republican New Jersey Governor Chris Christie’s term expires in January, then Christie would name his replacement.