“I do not believe we need to hear from an 18th witness,” the Colorado Republican told Colorado Politics in a statement. “I have approached every aspect of this grave constitutional duty with the respect and attention required by law, and have reached this decision after carefully weighing the House managers and defense arguments and closely reviewing the evidence from the House, which included well over 100 hours of testimony from 17 witnesses.”

Gardner had previously been noncommittal about Democrats’ demands to call more witnesses, including Bolton, who writes in a forthcoming book that Trump told him he withheld military aid from Ukraine to pressure the country to investigate Democratic political rival Joe Biden.