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The state’s decision to kill straight-ticket voting could cut turnout in down-ballot races in the 2020 elections — even if more voters show up to the polls.

Sure, those additional voters will cast ballots for president and U.S. Senate. But voter interest and knowledge gets thinner and thinner as the ballots go on and on.

Without straight-ticket voting — where voters register support for all of their parties’ candidates with a single vote — down-ballot candidates will have to win with the support of the relatively few voters who make it past the marquee contests.

Two-thirds of Texans voted straight ticket in 2018. In 2020, candidates for offices like constable and justice of the peace will need all the help they can get from friends and family; it won’t be enough to rely on the straight-ticket voters.

In particular, Democratic candidates depending on a growing base of voters may suffer, according to a study done by the Austin Community College Center for Public Policy and Political Studies.

“Most analyses of the election contend that straight-ticket voting helped the Democratic Party candidates in certain types of counties — metropolitan and some suburbs,” authors Stefan Haag and Peck Young wrote. “And we agree that the increased competitiveness of Democrats in many counties was abetted by straight-ticket voting.”

It’s not so much that Democrats were depending on straight tickets for their strength; it’s that strong candidates at the top of the ticket — like Democrat Beto O’Rourke — were making it easier for the rest of the party’s candidates to win some votes.

Pity the Democrats if you’d like. The real sufferers will be anyone at the bottom of the ballot. It’s one thing for voters to know which party they like, and to vote for the flag when they don’t know the individual candidates. And it will always be possible to keep doing that, since the party is listed next to each candidate’s name. But it’s a lot easier to vote for a whole party at once than to vote one at a time for each of that party’s candidates.

“The greatest effect of the elimination of straight-ticket voting will probably not be the elimination of Texans voting for all candidates of one political party — the essence of straight-ticket voting,” the two wrote. “The effect will be that people will spend more time in the voting booth.”

The state doesn’t compile data on straight-ticket voting; that’s done by county election officials all over Texas. Young, who heads the ACC center, and Haag, a retired ACC professor, worked with their students to pull together information on 2018 voting — an election that produced narrower-than-normal Republican wins and some Democratic upsets down the ballot. It was also the last year of straight-ticket voting in Texas. Some highlights:

Two-thirds of voters in the 48 biggest counties in Texas cast straight-ticket ballots.

Those counties (out of a total of 254) accounted for 85.9% of the votes cast in last year’s race for U.S. Senate.

The straight-ticket split in that Senate race was pretty even in those counties: 49.8% Republican, 49.5% Democratic.

That slim Republican advantage appeared first in 2016 and persisted in 2018 — a break from the GOP success of the last two decades; in 2014, their last big election blowout, Republicans got 58.6% of the straight-ticket votes, compared with Democrats’ 40.7%.

More than half of the 2018 vote came from seven counties: Bexar, Collin, Dallas, Denton, Harris, Tarrant and Travis. In those counties, Democrats got 55.2% of the straight-ticket vote and Republicans got 44.1%.

In the top 25 counties, the study found 75.9% of ballots were cast straight-ticket and that Democrats outdid Republicans in 10 of those counties.

All of that explains why a Republican governor and a state Legislature with a Republican majority would end a voting practice that helped their party into power; that power was eroding, in favor of the Democrats. They saw the signs in 2016 and decided the next year to end straight-ticket voting in Texas.

But they delayed the start of the new law until after the 2018 election — when it contributed to their losses in down-ballot races for statehouse seats, judgeships and county offices.

Now it’s gone. Will that turn the tide?

Disclosure: The Austin Community College District has been a financial supporter of The Texas Tribune, a nonprofit, nonpartisan news organization that is funded in part by donations from members, foundations and corporate sponsors. Financial supporters play no role in the Tribune's journalism. Find a complete list of them here.

Editor's note: The story summary below the headline on this page has been updated. The original version didn't make clear that Texas lawmakers voted to remove straight-ticket voting in 2017 — before the 2018 elections.