With more than one in five registered voters already casting ballots, midterm election turnout of more than 48.5 million voters has surpassed the 2022 record four days before Election Day.

Democrats have a 12-point early voting turnout advantage, approaching the margins that presaged Joe Biden’s presidential victory in 2020.

That higher turnout bodes well for Democrats — but its predictive value is uncertain given changing voter behavior and the limitations of the available data. And the favorable national picture for Democrats obscures some encouraging signals for the GOP in key Senate battleground states.

“We know that early voters are going to be more Democratic. That’s been a feature of elections for a while now,” said Michael McDonald, who directs the University of Florida Election Lab. “On Election Day the electorate shifts very much in the red direction. So Democrats have to build up an advantage in the early vote just to withstand what’s going to happen on Election Day.”In 27 early-voting states that track voter registration by party, 44% of early in-person and absentee ballots have been cast or returned by registered Democrats. Only 32% have been cast by registered Republicans, according to data compiled by McDonald’s lab.

The Democratic turnout bump is most pronounced in states like Iowa, Kansas and Nebraska — Great Plains states that usually elect Republicans but have surprisingly competitive races for the US Senate. But in Florida, Michigan and Texas, there are hints that GOP voters are returning to early and absentee ballots that they had recently eschewed.

A decade ago, acceptance of early and mail-in voting was bipartisan. Then came the Covid-disrupted election of 2020, when wide swaths of Democrats adopted vote by mail as a pandemic precaution while many Republicans opted to vote in person on Election Day.

But with pandemic routines fading from memory, more Democrats are returning to the polls on Election Day and more Republicans are voting early, said Tom Bonier, senior adviser to TargetSmart, a Democratic data firm.

And voters across parties are less likely to vote by mail. McDonald said mail ballot requests are down in many states — in part because of a Florida law that now requires voters to make a new mail-in ballot request every two years. Those who do request mail ballots are returning them sooner and in greater numbers, but others are finding other ways to vote.

“They’re voting in person,” Representative Greg Landsman, an Ohio Democrat, told Bloomberg Television’s “Balance of Power” this week. “That speaks to some of the worries about this election and people wanting to make sure that their votes are counted.”President Donald Trump, blaming mail-in votes for his 2020 reelection loss, has vowed a crackdown on the practice. His attempts to have the US Postal Service pre-screen ballots for their validity have been blocked by courts, but congressional Democrats are investigating whether USPS is working to circumvent those court orders. Postal officials say they’re processing election mail as normal but encouraged voters to return their ballots early.

Voting by mail is highest among older voters, with 54% of the mailed ballots coming from voters aged 65 or older in 14 states where data are available.

Political campaigns like early voters because they allow candidates to bank their support, reducing the risk of missing out on votes due to bad weather, disasters or other unexpected events. And campaigns can focus their get-out-the-vote efforts on ensuring that lower-propensity voters show up on Election Day.

Early voting numbers have become a favorite source of intelligence for political junkies looking for signals beyond polls and prediction markets. But the data can be inconsistent and contradictory among states. And early voters tend to be partisans whose ballots were never much up for grabs. Here are some key takeaways from states with battleground Senate or House races: ► Georgia: Across the Deep South, high turnout by Black voters — fueled by a backlash to Republican attempts to gerrymander formerly majority-Black districts — has boosted Democrats. Nonpartisan election data firm L2 estimates a 14-point advantage for Democrats.

► Pennsylvania: In a state with a number of competitive congressional races, Democrats represent 65% of all early votes cast compared to just 25% for Republicans — the biggest Democratic advantage in the country. That trend extends even into rural western counties that have moved sharply toward Republicans over the last decade.

► Florida: With a surge this week in registered Republican voters showing up to early voting centers, the GOP has surpassed Democrats in early voting turnout. But the lead is still small considering the Republican registration advantage. Four years ago, Republicans had a 6.4-point advantage in early vote. Now it’s two points.

► Texas: A marquee Senate race between Democrat James Talarico and Republican Ken Paxton has already attracted more than six million early voters — 84% of the total turnout in the last midterm election. While L2’s models suggest a five-point advantage for Democratic voters, Republicans are over-performing compared to their representation in the electorate.

► Michigan: Another relative bright spot for Republicans comes amid a pitched battle between Democrat Abdul El-Sayed and Republican Mike Rogers for a Michigan Senate seat. Though Democrats outnumber Republicans in the state, L2’s models estimate that 30% of Republican voters have cast an early vote, compared to 23% of Democrats.

► Iowa, Kansas and Nebraska: Democrats are outnumbered in Great Plains states with surprisingly competitive Senate seats — but have been nearly matching or exceeding early turnout by Republicans.