At least in Collin Co., the so-called “Trump effect” was limited to Trump himself. Democrats gained some ground on Republicans in terms of straight-ticket voters, but full-ballot voters remained friendly to all Republicans not named Trump.

All five House districts featured at least a Republican and Democratic candidate, and the five Republican candidates – four incumbents and an open-seat nominee – combined won 67% of the vote from full-ballot voters, measured head-to-head against their Democratic rivals. Trump narrowly defeated Hillary Clinton, 51%-49%, head-to-head among full-ballot voters. The gap between the House Republicans and Trump among full-ballot voters ranged from 10 percentage points (Justin Holland in HD33) to 24 points (Reps. Matt Shaheen in HD66 and Scott Sanford in HD70).

All Republicans countywide, including Trump, enjoyed significant straight-ticket advantages, but a 37% increase in the number of straight-ticket Democratic voters cut that countywide advantage to 58K votes. Republicans countywide had a 72K-vote advantage in straight-ticket voting four years ago.

Four of the five House districts shifted toward the Democrats, at least in terms of straight-ticket voting margins, while Sanford’s district became redder.

Most of the Democrats’ gains occurred in HD66, held by Rep. Matt Shaheen (R-Plano), and HD67, held by Rep. Jeff Leach (R-Plano). Both had straight-ticket voting advantages of more than 6K votes this year, about half of their advantage in 2012. In HD66, 4,839 more voters cast a straight-ticket Democratic vote than in 2012, and the number straight-ticket Republican votes fell by 1,392. In HD67, an additional 4,239 more people voted straight-ticket Democratic than four years ago, and straight-ticket Republican voting was flat.

Shaheen and Leach were barely held under 60% head-to-head against their Democratic opponents in districts where Trump received 53% and 52% head-to-head against Clinton, respectively. Full-ballot voters in HD66 and HD67 preferred Clinton to Trump, giving her 58% and 54% of their vote, respectively. Shaheen received 66% of the full-ballot vote, so about a quarter of his full-ballot voters did not vote for Trump. Leach received 62% of the full-ballot vote, about 17 points better than Trump.

The four incumbents received a greater share of the full-ballot vote in their districts than Mitt Romney in 2012, and Holland was within a tenth of a percentage point of Romney’s performance in his district.

So it appears that Trump’s effect on Collin Co. Republicans was to depress straight-ticket vote totals, but no negative coattails adversely impacted candidates down the ballot. His effect on Democrats remains to be seen. Whether higher straight-ticket Democratic vote totals were the result of Trump, Clinton or demographic shifts requires further research.

Whether their momentum continues into 2018 and beyond is perhaps a bigger question. In each of the last two gubernatorial elections, the number of straight-ticket Democratic votes was about half of the preceding presidential election. Straight-ticket Republican votes fell, too, but not quite as much. Of course, those elections occurred while a relatively unpopular Democratic president held office.