“When a President exercises constitutional authority to nominate a judge for the Supreme Court vacancy, the Senate must decide how to best fulfill its constitutional duty of advice and consent," he said in a statement Monday.
He said that he would vote to confirm a nominee that meets certain criteria.
"I have and will continue to support judicial nominees who will protect our Constitution, not legislate from the bench, and uphold the law," he said.
Gardner's announcement marked a victory for Trump and Senate Majority Leader Mitch McConnell, R-Ky., who are staring down what will likely be a grueling confirmation process.
The Colorado Republican was one of the many in his party to oppose Judge Merrick Garland's nomination in 2016 -- something Democrats have used to accuse the GOP of hypocrisy in moving forward with a replacement for late Justice Ruth Bader Ginsburg.
Along with Sen. Susan Collins, R-Maine, and others, Gardner's support was under scrutiny as he faces a tough re-election bid this fall. With Gardner's statement, it appeared as though Senate Republicans had the votes to approve Trump's nominee, barring any major complications.
The Lincoln Project, an anti-Trump group of Republicans, reacted by claiming Gardner had just conceded his election.
So far, Senate Judiciary Committee Chairman Lindsey Graham, R-S.C., and his predecessor, Sen. Chuck Grassley, R-Iowa, have supported moving forward with Trump's nominee, despite previous statements indicating they might not.
Both McConnell and Graham, who opposed Garland's nomination, argued that despite both being election years, 2016 and 2020 differed in that both the Senate and White House are currently dominated by the same party.
On Saturday, Sen. Susan Collins, R-Maine, who is facing a testy re-election after her support for then-Supreme Court nominee Brett Kavanaugh, opposed voting on a new pick until after the election. Her colleague Sen. Lisa Murkowski, R-Alaska, said just a day later that her position hadn't changed since before Ginsburg's death, and that she would oppose voting on a new nominee before the election.
Still absent from the discussion is Sen. Mitt Romney, R-Utah, who released a statement on Ginsburg's death but omitted how he would handle Trump's nominee.
Trump said he had narrowed his choices down to at five potential nominees. He's expected to announce the next nominee on Friday or Saturday.