Originally Published: 21 OCT 22 13:59 ET

Updated: 21 OCT 22 15:37 ET

By Melissa DePalo and Ethan Cohen, CNN

(CNN) -- More than 5.8 million ballots have been cast across 39 states in the 2022 midterm elections, according to data from election officials, Edison Research and Catalist.

In the battleground states of Arizona and Pennsylvania, Democrats are far outpacing Republicans in pre-election ballots cast, according to data from Catalist, a company that provides data, analytics and other services to Democrats, academics and nonprofit issue-advocacy organizations and is giving insights into who is voting before November.

That's not a surprise, and these data aren't predictive of ultimate outcomes. In recent years Democrats have been more likely to vote before Election Day while Republicans have preferred to vote on Election Day.

It's too early to know how high voter turnout will be in this election cycle, but overall, early voting numbers remain on par with the 2018 elections, which had the highest midterm turnout in recent history.

In Arizona, ballots cast by Democrats make up 44% of the pre-election ballots cast, while ballots cast by Republicans make up 33%. That's similar to pre-election ballot returns at this point of the cycle in 2020, when Democrats made up 45% and Republicans made up 31%.

However, this is a recent shift in Arizona. At this time before the 2018 midterm elections, Republicans had returned more ballots, with a 46% share to Democrats' 34%.

The 2020 election, between the Covid-19 pandemic and efforts from former President Donald Trump and his allies to question the integrity of mail-in ballots, could have shifted how people vote.

Democrats' comfort with pre-election voting compared to Republicans' is on display in Pennsylvania -- a state with one of the most competitive Senate elections this cycle.

Of the more than 420,000 ballots cast in the Keystone State, 73% were cast by Democrats and 19% were cast by Republicans.

That's actually a slight improvement for Republicans compared to this point in 2020, when 75% of pre-election ballots cast were from Democrats and 17% were from Republicans.

Early in-person voting has begun in most of the states with competitive Senate elections including Georgia, Ohio and North Carolina. Nevada's early in-person voting begins on Saturday.

North Carolina held its first day of early voting on Thursday, and more than 186,00 ballots have been cast in the state. The North Carolina State Board of Elections reported that's an uptick from the number of early ballots cast through the first day of early voting in 2018, when just more than 155,000 ballots were cast.

After the first day of early voting, ballots cast by Democrats made up 42% of the pre-election ballot share, and ballots cast by Republicans made up about 29%, according to the North Carolina State Board of Elections.

A large share of the pre-election ballots cast in the Tar Heel state have come from unaffiliated voters. As of Friday, unaffiliated voters cast more than 29% of the pre-election votes.