Washington (CNN) About 18 million Americans already voted before FBI Director James Comey made the bombshell announcement that he found new emails possibly relating to Hillary Clinton's private server.

The numbers include some good news for Republicans in Ohio and Iowa, and good news for Democrats in Florida, Arizona and Colorado, based on a CNN analysis of the latest early voting data. These conclusions were formed by comparing today's partisan turnout to historical levels from past years.

Registered Democrats have also cast more votes than registered Republicans in North Carolina and Nevada, though there are signs that the leads they amassed last weekend have receded somewhat in recent days. That's because the gap between Democrats and Republicans in those states is narrowing.

These findings represent absentee ballots and early votes cast by more than 18.6 million Americans across 37 states where data are available. CNN has partnered with Catalist, a data company that works with progressive candidates and groups, to receive detailed early vote return information this year. Catalist's voter list connects returned ballots with demographic and registration information, such as party registration, gender and age, and allows a closer look at who has already cast a vote.

These are not results -- ballots aren't tallied until Election Day. But the findings provide clues on who is voting, and which party is turning out to vote. And while the numbers track voters' party affiliations, not all Democrats are voting for Clinton, and not all Republicans are supporting Donald Trump.

Here's a look at the early voting data from several battleground states:

Arizona

Registered Republicans took the lead in Arizona this week, edging ahead of Democrats who surprisingly maintained a narrow turnout advantage during the first two weeks of early voting.

But it's not all good news for the GOP: Their advantage today is about half the size it was at this point in 2012. Republicans are currently ahead of Democrats by 34,000 votes, or 3.6% of the vote. At this point in 2012, Republicans were ahead by more than 62,000 votes, which translated to a 9.7% lead.

More than 915,000 people have already voted in Arizona, an increase from this time in 2012. About two-thirds of all votes in the Grand Canyon State were cast early in the last presidential election.

Colorado

Colorado conducts its elections almost entirely by mail -- every registered voter has already been mailed a ballot, and they can send it in whenever they want before Election Day.

Registered Democrats continue to lead Republicans in terms of turnout -- an edge they've maintained since ballots started being returned. They're up about 27,000 votes, which is a significant turnaround from this time in 2012, when Republicans were leading by about 19,000 votes.

Republicans led at this time in 2012 but Obama ultimately carried the Centennial State, and the fact that Democrats are ahead at this point could be good news for Clinton. Some key Democratic groups, such as younger voters, wait until the last minute to mail in their ballots. In fact, 38% of all ballots returned have come from voters over 65, even though that age group was only 16% of the Colorado electorate in 2012.

Georgia

Georgia has crossed the 1 million mark in terms of ballots cast. More than 1,061,000 people have already hit the polls in the Peach State -- a spike of about 37% from this time in 2012.

Voters do not register with a party in Georgia, so it's impossible to know whether Democrats or Republicans are ahead in turnout. But the state does compile statistics on the racial breakdown of the voters. So far, the electorate is slightly less diverse than it was at this point in 2012. Turnout among white voters rose by about 3%, while turnout among black voters is down by about 4.5%.

About half of all voters in Georgia cast their ballot before Election Day in 2012.

Florida

Republicans continue to lead Democrats in Florida early voting by a very slim margin. Registered Republicans are ahead by about 13,545 votes, a smaller lead than they had one week ago.

This is still a decent showing for the GOP -- it's preferable to be ahead than behind -- but they are still behind their pace from 2008, the last year that comparable data is available. At this point in 2008, registered Republicans had a 44,000-vote advantage, which meant they were ahead by about 2.8%. But even with that advantage in the early vote, it wasn't enough for John McCain to carry the Sunshine State.

Florida currently leads the nation in terms of early turnout, almost 3 million ballots already cast. A majority of the state's voters went to the polls early in both 2012 and 2008.

Iowa

Iowans have been voting since September, and the data has been consistently good for Republicans. There are positive signs for the GOP because Democrats are underperforming compared to past years.

Democrats are winning the turnout battle, and are currently ahead of Republicans by about 39,000 votes. But that's a significant drop from their position at this point in 2012, when they led by 56,000. Democrats enjoyed a similar lead of about 50,000 votes at this point in 2008 as well.

Furthermore, the Democratic lead has been shrinking. They were up by 16% one week ago, but they're ahead by 10% today. This lag could give an opening for Trump to flip the state red this year.

Nevada

Democrats continue to lead early voting in Nevada about a week after in-person early voting kicked off.

The Democratic edge stands at about 26,000 votes. That's a good sign for Democrats up and down the ballot -- in addition to the presidential race, there are competitive Senate and House seats up for grabs.

Earlier this week, Democrats were doing better than 2012. But according to the latest data, they are now slightly behind that pace: They're up by 8.8% today, but were ahead by 9.3% at this time in 2012.

Almost 70% of all Nevada voters went to the polls early in 2012.

North Carolina

The Democratic advantage in North Carolina's early voting continues, but may be slowing down. They're up by more than 186,000 votes, which gives them a 15% lead over registered Republicans. This is the smallest lead (as a percent of the vote) Democrats have seen since early voting began October 20.

There are signs that Democratic turnout started strong but has sagged over time. According to data released last week, Democrats were ahead of their 2012 pace. Now they are slightly behind.

Turnout among African American voters in has apparently dropped. So far, black voters are about 23% of the early voting electorate. That number was 29% at this point four years ago.

More than 6 in 10 voters in the Tar Heel State cast early ballots in 2012.

Ohio

Republicans have a lead in Ohio, a pivotal battleground that is looking like a must-win state for Trump.

Registered Republicans are up by about 39,000 votes, an improvement from their position in 2008. Ohio reports party registration based on which party's primary a voter participated in, and 2008 was the last year when both Democrats and Republicans held contested primaries in Ohio.

About one-third of Ohioans voted early in 2012. That number is on track to be lower this year, a likely result of the Republican-led legislature scaling back the number of early voting days. That change was enacted in 2013 and is in effect for the first time in a presidential election this year.