WASHINGTON — The two dozen Democrats vying to take on President Donald Trump have raised an eye-popping $13.6 million from Texas so far this year, underscoring the Lone Star State's critical role in the 2020 presidential race.

That high-dollar sum — the most precise count to date — isn't just due to native sons Beto O'Rourke and Julián Castro, either.

While O'Rourke has dominated the field in Texas by raising at least $5.9 million, Castro and three other White House hopefuls — Vermont Sen. Bernie Sanders, Indiana mayor Pete Buttigieg and former Vice President Joe Biden — each brought in more than $1 million from the state.

Those standings come via a Dallas Morning News analysis of an unprecedented campaign finance database compiled and shared by the Washington-based Center for Public Integrity.

The nonprofit news outlet tallied, for the first half of this year, all Democratic presidential contributions disclosed on reports from ActBlue, a Democratic fundraising platform, or on candidate reports when a donor gave more than $200, but not through ActBlue.

All told, the Center for Public Integrity's database covers 94% of the money given to Democratic candidates so far this year.

Data from ActBlue is particularly critical because it provides granular detail, such as donors' names, addresses and professions, on small-dollar contributions that are not included in the candidates' filings with the Federal Election Commission.

The more precise tallies in Texas reinforce the trends evident in earlier data dumps: O'Rourke, the former El Paso congressman, remains a fundraising force in his home state. His rivals have also made headway in loosening that grip, at least among deep-pocketed donors.

But here are some further insights that the new data helps reveal about the Democratic fundraising battle in Texas, which is a donor-rich and delegate-rich state that's early on the presidential primary calendar:

On March 14, the first day of O'Rourke's campaign, the El Pasoan brought in a staggering $2.8 million from his home state.

That amount is more than double what any other Democratic contender raised in Texas for the entire first six months of this year. It's also more than what several presidential candidates raised nationally in this year's most recent quarter.

O'Rourke hasn't had a day like it since.

The ex-congressman saw another money spike in Texas toward the end of March, which marked the end of the first quarter reporting period. But his home-state fundraising started leveling off in April, reflecting his activity at the national level as the shine came off his high-flying campaign.

The early infusion is enough to give O'Rourke plenty of runway. He's also generally continued to pad his fundraising lead in Texas. But his long-term trend is something to watch.

Other Democratic contenders have had fundraising bursts of their own in Texas, albeit not of the magnitude of O'Rourke's.

Castro, a former San Antonio mayor and U.S. housing secretary, saw an influx of Texas donors at the end of the first quarter and again after a breakout debate performance in late June. Biden's tallies spiked after he entered the race in April. Buttigieg got a bounce as his national profile increased.

But just as noteworthy are the Texas performances of Sanders and Massachusetts Sen. Elizabeth Warren, who've seen steady growth over time.

One important factor could be that many Democratic donors are hedging their bets. An analysis by the Center for Public Integrity found that 1 in 5 Democratic donors nationally are giving to multiple candidates. That kind of trend extends to Texas, as well.

It appears that the largest overlap in the Lone Star State is between O'Rourke and Castro, who share approximately 4,000 donors, and then between O'Rourke and Buttigieg, who share an estimated 3,900 donors, according to the center's study.

Another key variable in Texas — and across the U.S. — is the average contribution size that candidates are receiving from Democratic donors.

The statistic is often shared by campaigns eager to tout their "grassroots" support. But it's notoriously difficult to replicate with campaign finance data due to the messy way in which contributions are recorded with the Federal Election Commission.

The Center for Public Integrity database allows for a rough approximation, thanks to their efforts to identify individual donors by their names and ZIP codes

That result is still imperfect. Names don't always match, given that a donor named "Johnathan" could also go by "John" or "Johnny." ZIP codes can also be tricky since a donor may list her home address in some instances and her work address in others.

Still, the resulting measure is useful as a relative marker between the top contenders.

In Texas, it appears that Biden is relying most on deep-pocketed supporters. On the other end, Sanders, who ran for president in 2016, and Warren, who went to college at the University of Houston, appear to lean most on a small-dollar donor network.

Texas has been a GOP stronghold for decades. But it's nevertheless remained fertile fundraising ground for national Democrats. That means it's unsurprising some White House contenders are finding financial success by tapping their Lone Star State contacts.

It goes without saying, though, that Texas is most essential to O'Rourke and Castro.

The two Texans saw the state account for a much bigger share of their overall fundraising totals than any other presidential hopeful. O'Rourke built a massive base in Texas after his record-setting Senate run last year, while Castro has long been a star on the state's Democratic scene.

Such reliance can cut both ways.

On one hand, it shows that those who know the two Texans best continue to support them. On the other hand, it could illustrate a need to expand the fundraising map in a presidential primary season that hits Iowa, New Hampshire, Nevada and South Carolina before it reaches Texas.

O'Rourke raised the most money outside of Texas in California ($1.3 million), New York ($873,000), Illinois ($304,000) and Florida ($295,000). After Texas, Castro's top fundraising states were California ($808,000), New York ($244,000), Florida ($123,000) and Washington ($108,000).

Both campaigns, while underdogs at this point, remain confident.

O'Rourke's team has hailed how he continues to bring in donors, even in Texas, who never before gave to one of his campaigns. Castro's camp, meanwhile, points to his growing success among small-dollar donors as a sign that his campaign is resonating with Democrats.