With a presidential election on the line in 2020, Georgia is switching to a new voting company, Dominion Voting Systems, that state evaluators ranked second-best and that critics said will leave elections vulnerable. Dominion, based in Denver, must rush to install 30,000 voting machines for 7 million Georgia voters before the March 24 presidential primary, the largest rollout of elections equipment in U.S. history. Most voters in Tuesday’s local elections will cast ballots on Georgia’s 17-year-old machines, and voters in six counties are testing Dominion’s machines. The company faces intense scrutiny in Georgia, one of the most competitive states in the nation entering an election year featuring President Donald Trump and two U.S. Senate seats on the ballot. The challenge for Dominion is to seamlessly introduce computer-printed paper ballots in a state criticized last year over allegations of vote flipping, missing voter registrations, precinct closures, long lines and voter purges. The swift transition to new voting equipment has raised eyebrows far from Georgia. “What Georgia is trying to do basically blows my mind,” said Dwight Shellman, an election official at the Colorado secretary of state’s office. His state adopted a Dominion system in 2016. “We had 2 1/2 years to do it, and it was challenging,” Shellman said. “I can’t imagine implementing the number of counties Georgia has in, what, two months? Three months?” Actually, the work will take eight months. But the challenge remains daunting.