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WASHINGTON — President Donald Trump's home county in Florida is planning to send vote-by-mail request forms to all of its voters, adding it to the list of Democratic population centers in swing states that have taken steps to expand ballot access during the coronavirus crisis.

Miami-Dade and Broward counties, as well as Palm Beach County, where Trump is registered to vote at his Mar-a-Lago Club, all plan to send vote-by-mail request forms to their voters. The three neighboring South Florida counties together account for more than a quarter of the electorate in the critical battleground state.

In Wisconsin, another key swing state, the Milwaukee Common Council voted unanimously Tuesday night to send absentee ballot applications and postage-paid return envelopes to all registered voters in the city after the state's troubled election this month may have infected some voters with the coronavirus, according to the Milwaukee Journal Sentinel.

State laws typically bar counties from sending absentee ballots to voters who have not requested them, so sending request forms is the next best thing.

Democrats across the country have been pushing to expand voting by mail in response to the COVID-19 pandemic ahead of the November election, but they have run into GOP opposition.

Trump has led the charge, claiming without evidence that mail ballots "cheat," even though he himself requested an absentee ballot from Palm Beach County to vote in Florida's March 17 presidential primary.

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Palm Beach County Supervisor of Elections Wendy Sartory Link, who was initially appointed to the position by Republican Gov. Ron DeSantis, told NBC News that her goal in sending request forms to every voter has nothing to do with politics.

"My goal is to get as many voters to vote in every election as possible, and if people are uncomfortable doing that in person, the best answer is to send a vote-by-mail request," she said.

She said voting by mail is safe and secure, despite what her county's most famous voter claims. "It's something that the president feels secure enough with that he voted with it himself, notwithstanding what his other comments may have been," she said.

The moves in Florida's three biggest counties and Wisconsin's biggest city could encourage GOP state leaders to expand voting by mail themselves to even the playing field between the heavily Democratic urban centers and Republican-friendly territory.

"If Democratic-leaning municipalities in close states make voting easier for the people living in those municipalities, then it's likely to lead to more Democratic votes statewide. In close states, that could make all the difference," said Josh Chafetz, a Cornell University Law School professor who studies constitutional law.

Republicans in state legislatures could respond to the moves, Chafetz said, either by trying to pass laws stripping cities of the ability to make voting easier or by making voting easier everywhere, "so as to make it easier for Republicans to vote, as well."

The first option probably wouldn't work in Wisconsin — along with other swing states, like Pennsylvania, North Carolina and Michigan, if cities there take similar moves — because it has a Democratic governor who could veto the Republican-controlled Legislature.

"So in many cases, the second option will be the most likely outcome, which means that voting-protective measures by a few cities could make voting easier for everyone in the entire state," Chafetz added.

There's some precedent for that.

In 2018, when the county that includes Seattle moved to provide a postage-paid return envelope to every voter in the liberal county, state officials responded by deciding to send postage-paid envelopes to voters everywhere in the state after Republicans and others raised objections about uneven treatment.

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"My concern is that you start treating voters differently," Republican Secretary of State Kim Wyman said at the time. "You are now giving one-third of the voters in our state the ability to return their ballot free, and the other two-thirds don't have that option."

Florida already allows anyone to vote by mail, and just under 30 percent of ballots were cast by mail in the 2016 presidential election. Volusia County, home to Daytona Beach, held an election entirely by mail last year to decide whether to impose a sales tax increase.

Wisconsin also allows anyone to vote absentee, but only a relatively small number of people have taken advantage of it until this month's election, when over half of all ballots were returned by mail.