CNN  — 

Republicans in Florida’s most populous county, Miami-Dade, are turning out to vote at a somewhat higher percentage than Democrats – causing uneasiness among some Democratic operatives.

Nearly 63% of the 428,000 registered Republicans in the county have voted so far, whereas about 56% of the county’s 634,000 registered Democrats have voted to date, according to state data. About 225,000 people with no party affiliation have also already voted in the county.

While more Democrats than Republicans have voted overall in Miami-Dade, the county is seen by Democrats as a region former Vice President Joe Biden must win by wide margins in order to offset voting in the state’s predominantly red regions.

Democratic worries come as both President Donald Trump and Biden vie for Florida’s 29 electoral votes, with each candidate holding a rally there Thursday as CNN’s Poll of Polls shows Trump lagging in the state at 46% to Biden’s 49%. Politico was first to report the concerns among Democrats.

Steve Schale, a veteran Democratic Florida strategist who runs a pro-Biden PAC, said, “I’d love to see Dade County jump up this weekend and I’ll feel better if it does.”

But Schale added that Black voters in the county tend to vote in-person closer to Election Day, so he expects a bump in turnout over the coming weekend. He added that Democrats have had strong turnout in neighboring Broward County.

State data show about 61% of registered Democrats in Broward have voted so far compared to about 56% of registered Republicans in the county.

Democratic data consultant Matt Isbell said he’s seeing a “lagging factor” among Democratic Hispanic voters in Miami Dade.

“I don’t have a good answer for why that might be. But that is certainly a factor at the moment that is giving Democrats a lot of worry,” Isbell said.

Like Schale, Isbell said he expects to see an uptick in Black voter engagement in coming days, but he also said the dynamics of this election, with the pandemic and the increase in vote-by-mail, make comparisons to previous election cycles and predictions difficult.

Steve Simeonidis, chairman of the Miami-Dade Democratic Party, said he’s not concerned. “We’re quite confident and quite comfortable from where we are sitting right now. We need to keep working to keep things going but we are in a good place.”

CNN’s Caroline Kelly contributed to this report.