In battleground Florida — a state President Donald Trump believes he must win next year to be reelected — the right and left are already in voter-registration mode to build their ranks.

Democrats have audaciously aimed to add 1 million people to their cause ahead of the presidential election. Republicans, meanwhile, have quietly shrunk Democrats’ numerical advantage below 244,000 voters for the first time since at least 1972.

Both parties are setting out early in hot pursuit of an estimated 4 million unregistered and eligible voters.

But the arms race isn’t only about out-organizing the opposition. Heading into 2020, both Democrats and Republicans are also shifting tactics to keep voters from joining the fastest-growing bloc in Florida: independents, whose meteoric rise has thrown a state known for razor-thin election margins even further into electoral uncertainty.

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Republican Party of Florida Chairman Joe Gruters, who said the ballooning number of independents makes them a “commanding presence” in 2020, is well aware of the trend. “We’re aggressively going after these new voters,” he said.

Democratic leaders are pounding home the same point.

“We can’t continue with the status quo,” said Scott Arceneaux, a former Florida Democratic Party executive who helped push Democrats’ voter advantage over Republicans to 560,000 during President Barack Obama’s 2012 reelection campaign. “You’re going to need to have a big partisan effort on behalf of the state party, and on behalf of the presidential candidates.”

The numbers show why party organizers are already in gear. At the beginning of August, there were 4.968 million registered Democrats in Florida, and 4.724 million Republicans. Voters without party affiliation stood at 3.616 million — a number that has exploded since George W. Bush won the presidency in 2000 by a Florida margin of 537 votes.

At the time, independents numbered about 1.5 million, equal to about 17 percent of registered voters in the state. Now they make up more than a quarter of the state’s voters — even though they can’t vote in Florida’s party primaries. And their numbers have risen at a rate equal to the combined growth of both the Democratic and Republican parties.

Much of that trend is organic, a product of frustration with America’s gridlocked politics, the coming of age of party-averse youth and an influx of Hispanic immigrants who lack historical ties to the political parties. Independents are growing in power and size across the country.

There may be another factor at play, too, though its influence is limited. Some election experts believe the rise of the independent voter in Florida is also due to the Democratic Party’s growing reliance on a network of nonprofits that register voters — and are prohibited by law from pushing ideology along with paperwork.

As the first teams of organizers begin to fan out across the state during what has traditionally been the sleepy off-season, Democrats and Republicans are hiring new employees and budgeting millions of dollars for voter registration.

And Democrats are calling on deep-pocketed donors to give up their usual tax-deductible donations to the nonprofits that register voters in nonpartisan efforts — often known by their federal tax code number, 501c3 — and divert some of their money to the state party or into independent “dark money” 501c4 political operations that, without disclosing donors, can push a partisan message.

Steve Schale, a Democratic strategist who led Obama’s 2008 Florida campaign, believes party registration has become one of the clearest indicators of which candidate will prevail in an election as the country becomes more polarized. Independents muddy the outlook, but Schale said that if Democrats want to win, they need to significantly outnumber Republicans, who have proven better in Florida at turning out their voters.

“If more of them vote than us, and we have less of us, then we’re always going to be threading a needle,” he said.

One Republican strategist questioned the wisdom of throwing more money and manpower into voter registration, believing that enthusiasm for the candidate will outweigh any amount of work by clipboard-holding community workers. State data also show that, even in peak years, voter registration drives only account for about a quarter of the voter applications.

Even so, Florida just saw three statewide races decided by less than 0.5% in November. Democrats aren’t willing to wait around until July for a Democratic nominee to rally disengaged voters. Nor are Republicans sitting idly while Democrats set out more than a year ahead of the election to register voters.

“We’re doubling and tripling our efforts,” said Gruters, the Florida Republican Party chairman. “They’ve helped us probably get more focused on this area, to tell you the truth.”

Since 2011, the Democratic Party has sent local election offices almost 10 times the 65,000 registration applications that the Republican Party of Florida has submitted. But this summer, for the first time since the state began tracking third-party voter registration organizations, the Republican National Committee signed up to register voters in the state. The Trump-affiliated America First Action Super PAC also established a Florida-specific voter registration organization on Aug. 15, called Florida First.

Gruters, a state senator and 2016 co-chairman of Trump’s Florida campaign, said the party has dedicated 16 employees to registering voters across the state, and hired Matt Parker, a field strategist who worked for Gov. Ron DeSantis’ campaign, as a $180,000-a-year registration director. Republicans also have been holding voter registration drives — including one in Pembroke Pines that drew some protesters this month because it was held at a gun show.

Even DeSantis, Florida’s Republican governor, is getting the state in the game. He announced Wednesday that Florida would join a multi-state electronic voting database that requires that member states send postcards to the homes of eligible but unregistered voters to tell them in a nonpartisan manner how they can register.

“Voter registration is a priority for all of us,” said Trump Victory spokesman Rick Gorka, “to ensure that we elect Republicans up and down the ticket in 2020.”

The Democratic activist base, on the other hand, is more fractured.

Hundreds of thousands of voters have been registered over the last decade by organizers representing the nonprofits that organize in minority communities and receive their funding from national donor organizations like left-leaning State Voices and America Votes. This year, SWAG, a network of nonprofits working in cooperation with former gubernatorial candidate Andrew Gillum, aims to register a whopping half-million voters — 300,000 more than the Florida Democratic Party hopes to register by the time Democrats select a nominee in July.

Most that work will be nonpartisan, leaving voters to choose a party — or none at all — on their own. But, depending on the amount of money that Gillum is able to raise and dole out as he pursues an overall goal for the party of registering 1 million voters, the SWAG network expects to conduct more partisan registration through its dark money affiliates. (On Thursday, Gillum announced that he’s released $1 million to voter registration organizations.)

“We will be doing the largest [501]c4 registration we’ve ever done,” said Andrea Mercado, executive director of New Florida Majority, part of the SWAG network. “We think it’s important that we have some voter registration efforts where we’re pretty explicit about who we believe potential voters should be supporting.”

Jorge Mursuli, the voter registration guru tasked by Gillum with keeping in touch with dozens of independent operations registering voters, believes partisan registration will be crucial to defeating Trump.

Mursuli spent years leading Democracia USA, a nonprofit created to organize in Hispanic communities in battleground states. In Florida, he has helped register close to 100,000 voters, with the assumption that most would support Democrats even if they register as independents.

But it’s also true that an independent voter remains something of a wild card for the party. And Mursuli thinks Democrats need to be more aggressive in pushing new voters to register as Democrats if they’re going to beat Trump — one reason that Gillum is now steering resources into voter registration by 501c4 dark money groups.

“It’s not something that’s been done in the past but it’s very worth trying,” said Mursuli. “It’s going to be important for the country in terms of, ‘does this work?’ “

Still, left-leaning activist groups remain a force in the state, in part because they’re better able than political parties and campaigns to mobilize in communities and maintain lasting relationships. Tory Gavito, president of Way to Win, a donor organization that contributed $3 million toward nonpartisan voter registration in Florida during the midterm elections, thinks Democrats will see better results if they reach voters early instead of showing up in communities only during election season.

“Our mistake on the Democratic side has been flooding Florida with millions upon millions of dollars in the last weeks of an election, primarily on TV” rather than trying to build deeper ties to minority groups, Gavito said.

Democrats say they’ve learned the lesson. Nonprofits like the Miami-based Florida Immigration Coalition have already sent organizers into the field, and dozens of new Florida Democratic Party staffers have fanned out across the state in minority communities. Juan Peñalosa, executive director of the Florida Democratic Party, says the party has registered more than 9,500 voters since June — more than it registered in the entire off-year ahead of last year’s midterm elections.

“We are seeing, in the age of Trump, an unprecedented level of interest,” said Arceneaux, the former Florida Democratic Party executive director. “People are just so much more amped because the president is in 100 percent campaign mode every day. We’ve never had that.”