Philadelphia voters can rest assured Jim Kenney really was reelected mayor this month, according to a squad of data and voting experts from around the country who ran a rigorous statistical test of the results Thursday. But while it’s no surprise that a Democrat won by 80 percentage points in an overwhelmingly Democratic city, it’s notable that the scientists were able to conduct such an audit in the first place. That’s because on Nov. 5, for the first time, Philadelphia used voting machines that leave a paper record of voters’ choices. As Pennsylvania’s counties roll out similar new machines required to create paper trails in time for the 2020 presidential election, the reported electronic returns can now be checked for accuracy. That’s an important change in a state that Donald Trump carried in 2016 by slightly more than 44,000 votes, or less than 1%. Pennsylvania is expected to be critical again next year. “We know we saw in 2016, everybody wondering, was this real, was this not real?” said Kathy Boockvar, secretary of the commonwealth, whose department oversees Pennsylvania elections. In 2020 and beyond, with what are known as risk-limiting audits, election officials will be able to confirm that the text of paper ballots lines up with what ballot-reading machines say. “The stakes are high, people are very passionate, and we have the paper that will be able to show the actual evidence,” Boockvar said. Officials hope the audits will make it harder for bad actors to tamper with the results. They also hope to increase public confidence in elections generally, following what U.S. intelligence agencies concluded was a systematic campaign by Russia to interfere in the 2016 election to boost Trump. (That campaign involved the dissemination of news and information Americans consumed, not the manipulation of actual votes or voting machines.)