Democrats for years have said Arizona was about to tip in their direction, and those hopes grew with President Trump in office — but the early evidence suggests they are struggling to grow.
The latest numbers from the state’s voting rolls show that while neither party is doing particularly well in winning over voters, Democrats have lagged behind, even as both parties gear up for a marquee U.S. Senate race and several crucial House contests next year.
The same trend is playing out in Florida, Pennsylvania and other battleground states where Democrats should have been growing their numbers in the age of Mr. Trump, but instead are stumbling.
They have lost 12,000 registered Democratic voters in Arizona since the presidential election, bringing the number down to 1.2 million. Republicans have lost just 1,000 voters and stand at nearly 1.4 million in the state.
Enrique Gutierrez, a spokesman for the state Democratic Party, chalked up the numbers to a cyclical trend and predicted support would pick up as the midterm elections approach.
“Democrats are excited,” Mr. Gutierrez said. “I don’t know if we’ll necessarily overtake Republicans in terms of voter registration, but I think we’ll definitely close that gap, and we’ll try our hardest to appeal to independent voters.”
Arizona is not alone.
In Pennsylvania, Democrats held a registration edge of about 800,000 over Republicans — 4 million to 3.2 million — as of Dec. 18. But the number of registered Democrats is down 4.5 percent, while Republicans have lost 2.4 percent.
In Florida, Democrats hold a registration edge, but their ranks also have also dropped at a faster rate.
As of Oct. 31, the number of registered Florida Democrats dropped 1.9 percent from last year to about 4.8 million. The number of registered Republican voters fell 0.6 percent, to about 4.6 million.
Nevada Republicans, meanwhile, have shaved Democrats’ edge from 119,000 voters in October 2016 to about 98,000 as of Dec. 1.
Former Rep. Thomas M. Davis III, Virginia Republican, said many registered Democrats are transient in nature and the changes might not necessarily be subtractions but shifts elsewhere.
Democrats did muster significant get-out-the-vote efforts in Alabama and Virginia, where they won decisive victories in statewide races in recent months, as well as in a handful of special congressional elections where they came up short by relatively narrow margins.
“So where there’s been an election to rally around, Democrats have probably done better,” Mr. Davis said.
Although it helps to have a bigger pool of voters, raw registration numbers might not necessarily be Democrats’ biggest issue heading into the election year, said Nathan Gonzales, editor and publisher of Inside Elections, a political newsletter.
“One of the challenges Democrats have had isn’t that there haven’t been enough Democratic voters — it’s that Democratic voters aren’t turning out in higher numbers in a midterm election,” he said. “I don’t think a drop in voter registrations spells the end of Democratic chances in 2018.”
Voters are also continuing a long-term trend away from the two major parties.
Democrats in North Carolina lost 3,829 registered voters from February to September. Republicans gained 9,241 and Libertarians gained 1,468, but unaffiliated voters grew by 47,099 registered voters, according to a report from the Civitas Institute, a right-leaning think tank in the state.
In Nevada, Libertarians gained about 700 voters compared with last year, even as thousands of Democrats and Republicans dropped off the rolls.
Bill Redpath, a former national chairman of the Libertarian Party, said the numbers can be tough to gauge because registrars in many states have been scrubbing their rolls as part of routine postelection maintenance.
“The increase during the second half of the year is quite mild, but it might be good that there’s an increase overall, given voter purging going on,” Mr. Redpath said.
“I think overall, there continues to be interest in a third alternative in the United States,” he said. “If things get bad enough, I suppose that people do something strategic like, ‘Oh, no matter what, we’ve got to get rid of Trump,’ or something like that, so I don’t know. It’s very difficult for me to gauge that.”