Texas Elections 2018 More in this series

On Tuesday, more Democrats cast primary ballots than Republicans on the first day of early voting in the 15 Texas counties with the most registered voters. That hasn't happened since 2008.

Fifty-four percent of the day’s 51,249 in-person votes in those counties Tuesday were cast in the Democratic primaries, according to the Texas secretary of state. In 2014, that number was slightly less than half, and in 2010, Democrats represented just 45 percent of first-day voters.

Meanwhile, the total combined first-day turnout in those counties was up by more than 10,000 compared to the last two mid-term elections.

It’s hard to know what is responsible for those numbers — or whether the trends will continue through primary election day. The growth in first-day turnout comes during a time of high motivation among Democrats across the country. But there aren't high-profile Republican primaries for governor or U.S. Senate in Texas this year.

Also, the state's urban centers tend to lean more Democratic, so it's unclear whether the numbers are similar in more rural counties.

Strong primary turnout for one party doesn’t necessarily replicate itself in a general election. The last time Democratic voters outnumbered Republicans on first-day voting in primaries was 2008 during a heated presidential primary between Barack Obama and Hillary Clinton. Republicans still swept the state that year.

Still, some of Tuesday's numbers have Democrats excited.

In 2010, 15,523 Democrats in the top 15 counties voted on the primary’s first day of early voting. This year, that figure has nearly doubled, to 28,475. Republican first-day turnout increased over the same period, but only by about 4,000 voters.

In Harris County, home of Houston, Democratic turnout was up 200 percent from 2014, while Republican turnout increased by 25 percent. And in Dallas County, Democratic first-day turnout grew 56 percent from 2014 to 2018, while Republican first-day turnout shrunk 19 percent.

Texas provides for nearly two full weeks of early voting before the state’s official primary election day March 6. In 2014, nearly 600,000 total votes were cast in early voting.