Portman says he stopped at six polling places in the poorer suburbs of Kiev. He was looking for interference with the commissions running polling places, voter rolls, and secret ballots.
Portman said the polling places he observed ran smoothly.
"I did see people having to wait," he said. "I saw nobody leaving, because people were so eager to cast their vote, and to have a say in the future of their country."
Portman says he had a chance to meet winning presidential candidate Petro Poroshenko the night before the election. But he declined, to avoid making it look like the U.S. favored a candidate.
"What we favored was a fair process," he said.
Portman says he’ll redouble efforts to increase U.S. sanctions on Russia, allow U.S. natural gas exports to Europe, and sharply increase the U.S.’s supply of defensive weapons to Ukraine.
The senator spoke from Warsaw, Poland, where he met with officials about the Ukraine crisis, as well as U.S. service members stationed there following Russia’s annexation of Crimea.