Florida Gov. Rick Scott's refusal to extend his state's deadline for voter registration in response to Hurricane Matthew is leading to fears that perhaps tens of thousands of Floridians could be kept from registering, potentially impacting the presidential race.

The deadline to register is Tuesday, but with 1.5 million Floridians under mandatory evacuation orders, the Hillary Clinton campaign had urged Scott to extend it. He declined.

“Everybody has had a lot of time to register,” Scott, a Republican and staunch Donald Trump supporter, said Thursday night. “On top of that, we’ve got lots of opportunities to vote: Early voting, absentee voting and Election Day. So I don’t intend to make any changes.”

Asked at a Friday morning appearance whether his decision was aimed at helping Trump, Scott said: "I'm focused on a storm. I"m focused on making sure ... you don't lose a life."

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Barbara Goodman, the president of the Florida League of Women Voters, said her organization was "extremely disappointed" in Scott's decision, especially his apparent failure to consult with local election officials before making a decision.

"What is the harm in extending voter registration in these areas?" asked Goodman, who lives in Palm Beach County and said she'd lost power at her home. "Why would he not be open to that?"

"If he continues to stand on this ground, we do see it as voter suppression," Goodman added.

Asked whether Scott consulted with local election officials before making his decision, his office did not immediately respond.

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Georgia and South Carolina, the two other states most directly affected by Matthew, both have extended their deadlines to register.

NBC News, in partnership with the voter file company TargetSmart, analyzed data from 2012 for the 12 Florida counties that were evacuated due to Hurricane Matthew. During the final week of registration that year, 24,656 new Democrats registered, compared to 10,322 new Republicans. There were 21,485 registrations for "no party."

Dan Smith, a University of Florida political science professor and Florida election data expert, did not mince words when asked whether it appeared Scott refused to extend the voter registration deadline for partisan reasons.

“Absolutely,” he said.

Smith added that his research has found that individuals who register immediately prior to an election turn out to vote “at rates very comparable, if not higher, than the average registrant.” That makes this voter registration window key for turnout targets for both parties, but particularly so, Smith said, for Democrats, because of the demographic groups that take particular advantage of late registration.

They’re often people of lower socioeconomic status, who didn’t register at the DMV because they don’t have cars or drive. Or they’re young voters who didn’t make registration a priority. Or they’re newly-naturalized citizens who didn’t want to wait in line to register to vote after their naturalization ceremony. In short, likely Democratic voters.

"It’s a whole swath of individuals, many of them are going to be lower socioeconomic, tend to be younger and tend to be minority. And as a result, they disproportionately do register as either Democrats or no-party affiliates and we know that just by going back and looking at previous records,” Smith said.

That's not the only reason to think that the storm's impact would hurt Clinton. Progressive groups were in the midst of a major registration drive when the storm hit, many of them targeting minorities.

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"We're on a massive voter registration intake right now," said Goodman, whose organization is non-partisan. "It's come to a grinding halt in these coastal areas."

And three of the counties most affected so far — Miami-Dade, Broward, and Palm Beach — are Democratic strongholds, though others further up the coast are Republican-leaning. Strong turnout in those Democratic counties would be crucial to Clinton's chances of winning the state.

That’s not to say Scott’s move won’t impact Republican registration drives — Matthew looks likely to impact some heavily Republican counties, like Brevard, which is currently getting hit, and possibly Clay, Flagler and Duvall counties as well. But overall, late registration benefits Democrats disproportionately, so the political gamble Scott is making may be aimed at trying to hinder their edge.

There may be a loophole that allows both Republican and Democratic groups to continue registering voters through the final days of the window. Florida state law requires third-party voter registration groups to turn over any applications they collect within 48 hours after they’re completed, or the next business day “if the appropriate office is closed for that 48-hour period.” Still, that option is likely to mitigate only a small share of the impact on registration, election experts say.

Polls currently give Clinton a slim lead in Florida, which is seen as the most likely single state to determine the presidential election, as it did in 2000. In 2012, President Obama won the state by just under 75,000 votes.

There's already talk that Scott's decision could trigger litigation. Marc Elias, a Democratic election lawyer who this cycle has brought several lawsuits against restrictive state voting policies, tweeted Thursday night:

"Gov. Scott is awful. Is disenfranchising voters really the GOP's only strategy to try to win? Sadly it seems so."

Gov. Scott is awful. Is disenfranchising voters really the GOP's only strategy to try to win? Sadly it seems so. https://t.co/y90nk0upPU — Marc E. Elias (@marceelias) October 7, 2016

Elias, who also is working with the Clinton campaign, did not respond to an inquiry on whether he will sue to force Scott to extend the deadline. It's not clear whether Scott even has the authority to do so, since Florida law gives the state legislature the power to set election rules.

Scott has come under fire in the past for restrictive registration and voting rules. In 2012, a court blocked a state law that severely limited the activities of third-party voter registration groups, leading some to leave the state entirely. The same year, courts also put a stop to a flawed purge of the rolls conducted by Scott's administration, which led to numerous eligible voters being removed. And cuts to early voting backed by Scott led to all-day lines at some heavily minority polling places on Election Day in 2012. The cuts were reversed the following year.

"The Governor of Florida, Rick Scott, announced that there had been no fatalities reported in his state at the time of the briefing, but warned that Florida is still facing strong storm surges."