Democrat Mark Kelly opened a big lead Tuesday against Republican Sen. Martha McSally in early election results for an Arizona race that will be crucial in determining control of the U.S. Senate. Democrats are optimistic that Arizona's changing demographics and President Donald Trump's unpopularity among some suburban voters can push retired Kelly, a retired astronaut, to victory in Tuesday's election. He is the husband of former U.S. Rep. Gabrielle Giffords, who was injured in an assassination attempt in Tucson in 2011. Kelly led 55% to 45% with 75 percent of the expected votes counted. The tally includes early votes cast through the weekend, and the race will likely tighten as officials tally Election Day votes, which are expected to favor Republicans. Kelly all but declared victory, saying: “I’m confident that when all the votes are counted, we’re going to be successful in this mission.” “The work starts now. And we desperately need Washington to work for Arizona,” Kelly told a small group of family and reporters in Tucson. “My top priority is making sure we have a plan to slow the spread of this virus, and then getting Arizona the resources our state needs right now.” After his speech, Kelly clasped arms with Giffords and his two adult daughters as a massive screen behind him showed video feeds of supporters cheering from their living rooms. McSally was not expected to speak Tuesday night. She expressed confidence Monday to supporters that she could win. No matter who wins, Arizona will have a senator from Tucson for the first time since Democrat Dennis DeConcini left office in 1995. An influx of new voters in the fast-growing suburbs of Phoenix and extensive get-out-the-vote effort in the Latino communities in Phoenix and Tucson helped put Arizona, a longtime Republican stronghold, in play for Democrats. The trend accelerated with a shift away from the GOP among white suburban women who turned against Trump. The 2018 victory of Sen. Kyrsten Sinema, the first Democrat to win an Arizona Senate seat in 30 years, over McSally illustrated the changing nature of the state. After her defeat, Republican Gov. Doug Ducey appointed McSally to McCain’s former seat in 2018.