Washington (CNN) With exactly one week until Election Day, at least 20 million people across the country have already cast their ballots for the midterms as of Wednesday morning.

CNN is partnering with Catalist, a data company that works with Democrats and others, to compile counts of ballots cast before Election Day, either early in-person or by mail.

Below is a breakdown of how votes are coming in from seven critical states, and how tallies from this year compare to the 2014 and 2016 cycles. In some states the analysis includes a dive into ballots cast by party registration and demographics available through each state's voter file. Catalist compiles these data by matching ballot request and return data from official sources to their database of voter records. This allows for analysis of ballots returned based on voters' partisan affiliation and certain demographic traits.

So far, some emerging themes are clear: more women than men have voted. And the early vote is also predominantly older in the seven states, although a higher percentage of early voters are often older.

And states are already surpassing their comparable early voting totals from at this point in 2014, the last midterm election that did not coincide with a presidential election.

Although the turnout in 2014 was historically low, the lowest in 70 years according to the United States election projec t, and the map of competitive races in 2014 do not match where the battles are being fought this cycle, some states are approaching presidential levels of turnout.

Arizona

The Grand Canyon State is home to a historic toss-up Senate race -- Rep. Kyrsten Sinema and Rep. Martha McSally are vying to become the first woman senator to represent Arizona. It also has five key House races across the state. Five of the state's nine congressional districts are also competitive, according to CNN's Key Race ratings.

According to an NBC/Marist poll out Tuesday, Democrat Sinema tops Republican McSally by 6 points. In terms of fundraising, Sinema and McSally are neck and neck -- both have raised over $3 million and spent over $4 million according to the most recent FEC filings.

Arizona has already surpassed its comparable early voting total for this point in 2014. Nearly 1 million ballots have been cast to date in Arizona, according to Catalist.

The state, which Trump carried by 3.6 percentage points in 2016, had among the closest gender parity in its early voting of any state in this analysis -- about 52% were women, 48% men.

(Registered voters in the state overall are 35% Republican, 30% Democratic and 35% registered without a party affiliation or with another party.)

But Arizona also has one of the lowest shares of young people making up its early tallies so far, with voters under 30 making up about 6 percent. By contrast, older voters dominate the early vote, with nearly three out of every four votes cast coming from those over 50 years old. Nearly half of all votes are attributed to those 65 and up.

Arizona is one of the states where party registration is made available for early vote tallies. These numbers reflect a count of the voter's party affiliation, but do not indicate who a voter actually chose on the ballot.

So far, 34 percent of votes have been cast by Democrats and 43 percent by Republicans. Additionally, independent voters accounted for 18 percent of ballots cast, with another eight percent recorded as "unknown."

Florida

The tossup Senate race between Democratic incumbent Sen. Bill Nelson and Governor Rick Scott is the most expensive Senate race in the country, with Scott pouring huge sums of his own money into his campaign.

Out of the state's 27 seats in the House, there are two toss-up races, and three CNN rates as likely Republican.

The gubernatorial matchup is also one of the most closely watched in the country: Tallahassee Mayor Andrew Gillum, the Democratic nominee, takes on Republican and former Rep. Ron DeSantis

Over 3 million votes have been cast ahead of the 2018 midterms so far, the Catalist data shows, surpassing what was reported at this point in 2014.

In 2016, Florida ended their early vote period with a record 6.6 million votes, equivalent to about half of the state's nearly 13 million voters. About 70% of those had already been cast at this point in 2016, suggesting this year's tally will be significantly lower, if early voting is proceeding at a similar pace.

Examining the early votes cast by party registration in the state, 40% have been cast by Democrats and 42% by Republicans. Roughly 18% of the votes have been cast by those with no party affiliation.

So far, more women than men have voted early, the data shows. About 1.6 million, or 54% of early voters, have been female. Florida early voters also skew predominantly older, so far. Similar to Arizona above, three out of four are over 50 years old.

CNN's most recent polling shows Nelson with just a two-point lead over Scott, and Gillum and DeSantis also in a dead heat, with Gillum up by one point.

Nevada

Republican Senator Dean Heller is considered one of the most endangered Republican incumbents heading into election night, and the state is also home to two House races that are leaning toward Democrats.

Hillary Clinton ended up carrying the state by 2.4 points in the 2016 election, a fact that Democrats looking to make inroads in the state hope bodes well for them. The most recent polls conducted by CNN have Heller and Democrat Jacky Rosen nearly even, with Rosen leading by three points. While Rosen has spent nearly $7 million throughout her campaign, Heller has spent close to $2 million.

Nevada has exceeded its 2014 early vote totals to this point. Nearly 290,000 votes have been cast so far in the Silver State, the data shows, with roughly 40% cast by registered Democrats and 38% by Republicans. Independent voters account for approximately 14%.

Nevada has a similar gender breakdown to Florida so far, with women casting at least 150,000 or 53 percent of early ballots.

Nevada has seen more young voters cast early ballots than Florida or Arizona. More than seven percent of early votes have come from people under 30.

Other races to watch

In Georgia, where Democrats have alleged a Republican campaign of voter suppression, and Texas, where Rep. Beto O'Rourke hopes his eye-popping fundraising can help unseat Republican Sen. Ted Cruz, the number of young voters turning out is a noticeably higher percentage than in the states mentioned above.

The data shows over 10% of early Texas voters are under 30 years old.

In Georgia, 9% of early votes are coming from those under 30.

About 1.3 million ballots have been cast in Georgia so far, and all eyes are on the race for governor between Democrat Stacey Abrams and Republican Brian Kemp that has become a microcosm of the national political climate. Abrams is running a liberal-leaning campaign to be the nation's first black female governor, and Kemp is effectively running on President Donald Trump's agenda.

The early voting total in Georgia now has far exceeded its 2014 totals to this point and is even approaching the 1.6 million votes cast in 2016 by this point.

Women have accounted for 56% of Georgia's early vote so far.

In Texas, where of more than two million ballots cast so far, women also represent a majority with 54% of the early vote. Texas has also outpaced its totals for 2014 to this point and is approaching the early votes it was reporting in 2016.

In the Senate race between Cruz and O'Rourke, currently rated to lean toward the Republican, CNN's latest polling has Cruz ahead by an estimated seven points. The state is also home to five competitive House races out of its total of 36, and a governor's race where the Democratic candidate, Lupe Valdez, is running to be the first out LGBTQ and Latina governor.

In Tennessee, Democrats view the Toss Up Senate race between Democratic Governor Phil Bredesen and Republican Rep. Marsha Blackburn, as crucial if they are to overtake the Senate majority. The most recent CNN poll has Blackburn leading Bredesen 49% to 45%.

There have been more than one million ballots cast, 54% by women, and about 70% overall by voters 50 and older.

In Montana, at least 220,000 votes have been cast early, with about 52% by women and 71% by those 50 or older.

Republicans view that seat, currently held by Democratic Senator Jon Tester, as one of their top targets this cycle. Tester became unpopular with President Trump after their infamous feud and the Trump carried the state by twenty points in 2016.