Early voting numbers are rolling in, and campaigns are claiming their early voting victories.

Clinton looks like she is up in Virginia and North Carolina — on track to have higher numbers than President Barack Obama did in 2012. Iowa and Ohio look better for Donald Trump than they did for Mitt Romney, and voting registration has evened out between parties in Florida, a state where absentee voting has typically swayed Republicans. Looking at the numbers in swing states, things are looking up for the Clinton campaign; CNN reported that Clinton’s numbers in Arizona — which are also better than Obama’s in 2012 — might bring the typically red state into play as well.

University of Florida voter turnout expert Michael McDonald concluded for the Huffington Post that early voting results seem to be consistent with what polling has been telling us so far: Clinton has a slight edge in Florida and North Carolina, and has a bit of a sore spot in Iowa, where Trump is currently leading by 3.7 points, according to the RealClearPolitics average.

In other words, “despite weakness for Clinton in the Midwest, Clinton looks well-positioned in other states Trump still needs for an Electoral College victory,” McDonald writes.

These are good signs for Hillary Clinton: Early voting is beginning to reflect her lead in the polls. But it’s important to remember not to read too much into early voting numbers; they give an incomplete, and at times misleading, picture of the election. They are, however, a good judge of voters’ eagerness and decidedness, which can be a source of encouragement — or discouragement — for campaigns.

Early voting is a good measure of enthusiasm

Early voting is usually a good measure of enthusiasm; lots of early voters means lots of decided voters.

Democratic early voting surged in North Carolina after the in-person voting period opened on October 20. Democrats led Republicans by more than 13 percentage points by the end of October 23, which could indicate that “there may be some lack of enthusiasm in North Carolina for the Republican ticket,” according to Paul Gronke, the director of Reed College’s Early Voting Information Center. However, Gronke says at this point the differences in actual ballots are “marginal.”

While Republicans still have a slight edge in voting registration in Florida (42 percent to Democrats’ 40 percent), it is a very preliminary indication that Florida may not be seeing the new Republican voters the Trump camp might have hoped for. It’s “a good sign for Clinton in a state that was extremely close in 2012,” Barry Burden, an early voting expert and political scientist with the University of Wisconsin Madison said. (Especially as it becomes increasingly apparent that the Trump campaign did not push mail-in ballots with the Republican electorate.) Currently, Florida Republicans lead Democrats in returned mail-in ballots at a much smaller margin than in 2012.

And while there doesn’t seem to be much enthusiasm for either candidate this year, there is some speculation that people voting against the opposing candidate rather than affirmatively voting for their candidate might bring people to the polls.

When the early voting periods were about to open, McDonald told CNBC he was watching the Hispanic and rural white vote. "There is speculation that Trump's rhetoric could entice Hispanics to vote against him, and there is some evidence in polls that Hispanic voting enthusiasm is running higher than normal," he told CNBC.

The same theory can be applied with other demographics of voters, Gronke said.

"Trump continues to make statements that alienate African-American voters, and he struggles to get beyond 2 percent in some state polls. Under that circumstance, and faced with a well-oiled Democratic [get-out-the-vote] machine, why would African-American voters wait?" Gronke told me in September, noting that Trump also doesn’t seem to have much of an early voter ballot-chasing operation.

"All of this might lead to an early electorate that is even more Democratic and more diverse than in the Obama elections — but all of this is contingent on all kinds of assumptions," Gronke said.

There are limitations to reading early voting tea leaves

It’s important to remember — and a general scan of contradicting headlines on early voting from the New York Times to Fox News will show you — that it’s still early to say definitively that these early voting numbers indicate final results:

“It is quite difficult to discern what the election results will be from early voting numbers,” Burden said. “The patterns do not tell a coherent national story. … Ballots are coming in at different rates for the parties in each state. The messages appear to differ from one state to the next.”

And as McDonald warns in his weekly update on the early voting numbers for Huffington Post: “These are still early hints of the direction of the election. There is still much time left in the election, and these numbers can be affected by how election officials run the election, campaign strategies to mobilize voters, and voters’ behaviors.”

There are a lot of limitations: States reporting early voting totals don’t always include all counties; some states require party registration, like North Carolina, while others, like Wisconsin, don’t; and numbers derived from party registration are fallible. These distinctions can explain some of the early results. While Clinton is outperforming Trump in Nevada, the state might favor Democrats because of the concentration of early voting data coming from Clark County, where Las Vegas is, and Washoe County, where Reno is (two Democratic-leaning regions in the state). Things in Ohio might be looking up for Trump because there isn’t as much of an early voting history in Democratic counties, Burden explains.

University of Denver political scientist Seth Masket crunched the numbers for FiveThirtyEight on how well early voting numbers predicted the final tally in past elections. He simply concluded, “The relationship is positive, but it’s pretty noisy. In other words, knowing how a party is doing in early voting doesn’t tell you much about how it will do once all the votes are counted.” In fact, he found that looking at early voting numbers in 2012 would give you “wildly misleading” results:

Democrats maintained substantial leads among early voters in North Carolina, Louisiana and West Virginia, and were trailing by a relatively narrow margin in Oklahoma, but still lost those states when all the votes were counted. Republicans won early voters in Pennsylvania and Colorado but lost the final tallies there. Maryland was a safely Democratic state in 2012, but the 75 percent of the early vote that went the Democrats’ way was a far cry from the 63 percent of the total vote they won once voting was finished.

But early voting numbers confirming early polling is a good sign — and while there are a lot of factors to take into consideration before drawing conclusions, the numbers are positive indications for Clinton, especially taking past early voting trends into consideration.

We have seen a shift in early voting demographics

Put simply: Early voters are decided voters, Gronke told me when early voting started in September. "Individuals who cast an early ballot make up their minds early," he says.

There has been a shift in early voting demographics in the past two decades. "Prior to 2008, these ‘decided’ early voters matched demographic patterns that are well-established in American politics," Gronke said; they were older, educated, wealthier, ideological, and highly partisan. And for the most part, particularly with mail-in voters, these early voters mostly leaned Republican, which can also be attributed to a strong GOP push for mail-in absentee voting in the 1990s and 2000s. Meanwhile, in-person early voters tend to lean more toward Democrats. North Carolina this year is a good example of how this plays out — Republicans led mail-in voting, and Democrat early voting turnout shot up when in-person voting windows opened.

Barack Obama’s presidential campaign made a big stride with Democratic early voting in 2008, targeting areas with higher Democratic voter potential — areas that also had higher populations of African-American voters. Black churches used Sunday services to push people to the polls in what they called "souls to the polls" initiatives, University of Wisconsin’s Burden recalls.

It was wildly successful. In North Carolina in 2008, more than 70 percent of African Americans voted during the early voting period, Jennifer Clark, counsel at New York University’s Brennan Center for Justice, said — a trend that continued into 2012. Early voting in North Carolina is running slightly behind the pace of 2012, according to McDonald’s analysis.

While African-American voters were not typically billed as early voters, Gronke notes that black Americans fit the behavioral profile of a "decided voter."

"There was very little that would change the minds of many African Americans, particularly in 2008, when they had the first opportunity ever to cast a ballot for an African-American presidential candidate," Gronke said. "Why wait?"

Some argue that early voting "limits the set of information available to voters," as Eugene Kontorovich and John McGinnis wrote at Politico, but Clark says "that argument tends to not give voters enough credit."

Some states opened early voting windows more than a month before Election Day — some before presidential debates — but most early voting happens closer to Election Day and after debates.

According to Gronke, who said he asks survey questions on this regularly, there is "virtually no evidence of ‘voter regret.’"

Early voting is a growing and popular trend, but it’s still unclear whether it helps voter turnout overall

There are clear reasons why voters like early voting reforms: There are long lines at the polls on Election Day, and early voting expands voters’ options, especially when it comes to missing work or school.

But there are also political and administrative incentives for early voting, Burden said.

"Voters like it — politicians like to make them happy, and the party and candidates like early voting because there is the certainty of banking voters before Election Day," he said, noting that early voting is likely less of a hassle and less expensive for polling administrators.

Whether it is an effective way to get out the vote is still up for debate. Burden’s research found early voting actually decreased turnout, and the surge in 2008 has remained relatively stagnant since, possibly implying it might have had more to do with the candidate than the actual voting reform.

Burden attributes the decrease in voter turnout to a "dilution of the power of Election Day" — that having many days of voting reduces the pressure to vote altogether.

But not everyone agrees. Gronke's study cites research showing the opposite — early voting can increase voter turnout by 2 to 4 percent, especially when offered with accessible polling places and after-work and weekend hours, Clark adds. So it may matter more how early voting is implemented than purely whether the state offers it.

Either way, turning back now would be more disruptive than just expanding the practice, Burden said.

"There is an asymmetric effect," he said: With more and more people using early voting and liking it, rolling back early voting would do more harm to turnout.

There has been some controversy over early voting — but mostly in swing states

There has been tremendous growth in early voting opportunities in the past two election cycles — 37 states and the District of Columbia offered some form of early voting this year. Even so, there have been attempts to roll back the reform.

Proponents of early voting say it’s just a bipartisan debate and that the arguments against early voting hold little water.

"There is nothing about the policy that is intrinsically Democratic or Republican, because we see this became popular regardless of the political leaning," Clark tells me. The controversy comes with where these rollbacks are happening: swing states.

States like North Carolina and Ohio have become early voting battlegrounds, where Republican-controlled state legislatures have tried to cut in-person early voting days, which tend to favor Democrats. Advocates for reducing early voting argue it leads to more voter fraud, though there is no substantive evidence that voter fraud is a problem. In 2014, the US Government Accountability Office concluded that the rate of voter fraud is between 0.1 percent and zero percent.

And according to Clark, voter fraud is more common with mail-in ballots — which are not being contested — rather than in-person voting. In North Carolina, Republican lawmakers were even making the argument that voters could die between their early vote and Election Day.

There’s also some explicit evidence of the partisan politics behind these efforts, after a GOP consultant told the Washington Post that the push in North Carolina was to minimize African-American Democratic voters.

"Look, if African Americans voted overwhelmingly Republican, they would have kept early voting right where it was," the consultant, Carter Wrenn, said. "It wasn’t about discriminating against African Americans. They just ended up in the middle of it because they vote Democrat."