Actually, that's not true.
People have to be pardoned all the time who were wrongly convicted. A Chief Executive CAN pardon someone who MAY have committed a crime from "all crimes he may have committed." Andrew Johnson pardoned an attorney who sided with the Confederacy of crimes he "may" have committed. Ronald Reagan very seriously considered pardoning Oliver North and John Poindexter, neither of whom had even gone to trial at the time he was leaving office. He was talked out of doing it by his advisers, who said any pardon offered in those last hours would stain his legacy, a lesson lost on both Bush 41 and Bill Clinton.
It's just like treason - everyone uses it wrong to overstate the case.
Trump might have broken the law, but since we are NOT at war with Russia, Tim Kaine is an idiot for calling it treason. Even left-wing Vox admitted this recently.
https://www.usatoday.com/story/news...mit-treason-under-legal-definition/471533001/
Russia, as legal experts have noted, is formally at peace with the United States, so any actions taken with Russia would not technically be considered treasonous.