A letter written by Senate Republicans and Democrats in 2016 undercuts President Trump’s claim that while he was vice president, Joe Biden pressured Ukraine’s government to fire its chief prosecutor to protect his son, Hunter, from an investigation.

Biden says his motive was just the opposite: he accused Ukrainian Prosecutor General Viktor Shokin of failing to investigate deeply rooted corruption in the country — including his own office.

And the letter, found by a CNN investigative team, demonstrates that Biden had backing from Republicans as well as Democrats. It shows “that addressing corruption in Ukraine’s Prosecutor General’s office had bipartisan support,” the news network says.

The letter was sent to Ukraine by members of the Senate Ukraine Caucus. The signers included Republicans Rob Portman, Mark Kirk and Ron Johnson, and Democrats Dick Durbin, Jeanne Shaheen, Chris Murphy and Sherrod Brown.

Ukraine’s legislature voted to fire Shokin in March 2016, a month after the letter was sent.

Prior to that, in December 2015, Biden addressed the Ukrainian parliament, saying: “It’s not enough to set up a new anti-corruption bureau and establish a special prosecutor fighting corruption. The Office of the General Prosecutor desperately needs reform.”

Despite Trump’s claim, CNN says, “There is no evidence of wrongdoing by either Joe or Hunter Biden, nor is it clear whether Hunter was under investigation at all.”

CNN says its investigators reviewed hearings conducted at the time in the House and Senate and found that there was bipartisan “praise for Biden’s efforts from former members of George W. Bush’s administration and an Obama administration official who is now a nominee for an ambassadorship in the Trump administration.”

At a hearing in March 2016, John Herbst, former U.S. ambassador to Ukraine in the Bush administration, “testified that there was widespread support for the removal of Shokin and specifically praised Biden,” CNN says.

“Vice President Biden has been a great advocate for reform in Ukraine,” Herbst said.