Are Texas suburbs slipping away from Republicans?

By the end of Election Day, the political maps of the state’s suburban and swing counties had a peculiar blue tint.

The blue washed over the Dallas-Fort Worth area and crept up on suburban counties in North Texas. It spread from Houston — in a county that was once a political battleground — and crested over some of its suburban communities. And it swept through the Interstate 35 corridor from Travis County to its neighbors to the north and south.

Counties that haven’t voted for a Democrat in decades turned out for Beto O’Rourke in his unsuccessful bid to unseat U.S. Sen. Ted Cruz, and he picked up enough support in ruby red Republican counties to force Cruz into single-digit wins.

It could all be a blip — a year of Democratic enthusiasm spurred by a shiny candidate or vitriol toward President Donald Trump. But with margins narrowing over time in some of the GOP’s longtime strongholds, Tuesday night's results suggest that the Republican firewall in the suburbs could be cracking.

In Central Texas, O’Rourke broke the electoral status quo in Hays and Williamson counties, rapidly growing bedroom communities taking in new — likely liberal — residents from Austin.

Hays County, home to Texas State University, hadn’t voted for Democrats at the top of the ticket since 1992. But Republicans’ control of one of the fastest-growing counties in the country has been weakening for years. Last night’s results indicate the county is trending blue. It swung hard toward the Democrats, giving O’Rourke a 15.3 point margin and narrowly opting for Gov. Greg Abbott’s Democratic challenger Lupe Valdez despite the 9-point margin of victory Abbott claimed over Democrat Wendy Davis in 2014.

The flip to blue was less all-encompassing in Williamson County. O’Rourke claimed a 2.8 margin of victory, which was notable given how Republicans have long maintained a strong advantage there. Abbott easily held onto the county, but another statewide Republican — Attorney General Ken Paxton — lost there.

In a coup for Democrats, Tuesday night proved that Harris County has ceded its title of the biggest battleground in Texas. Democrats ended a long streak of remarkably thin electoral margins in the state’s biggest county in 2016 when it awarded Hillary Clinton more than a 12-point margin of victory. O’Rourke grew that advantage this year by several more points.

Perhaps more notable was O’Rourke’s performance in neighboring Fort Bend County, another suburb that had long been considered red but is in the battleground category now.

The most ethnically diverse in the United States, Fort Bend swung by 12 points in the Democrats’ column in 2016. It was an electoral flip that Democrats hoped would be a sign of things to come, particularly given that the county’s demographics could help it turn this diverse pocket of Texas reliably purple in the future. If Abbott’s razor-thin margin of victory — just .3 percent — and losses by other statewide Republicans are any indication, future elections don’t bode well for the GOP.

Beyond the boundaries of Dallas County, North Texas has long stood as a bastion of the GOP’s political strength in the state. But this year, O’Rourke cut into Republicans’ control in several of those strongholds.

O’Rourke narrowly flipped Tarrant County — considered the most conservative urban county in the country — with a .6 percent margin. It was a remarkable outcome in the third largest county in the state, but it offers no certainty for the long run.

Democrats have also been making gains in Collin County in the last few elections, with the results of their efforts exacerbated in the Trump era. The county easily stayed in the Republicans’ column, but Cruz’s 6-point margin of victory is a fraction of Republicans’ past wins.

In Denton County — just north of Tarrant — Democrats have steadily cut away at Republicans’ margins of victory in the last three elections. Trump’s 20-point margin in 2016 was already a drop from Abbott’s 32-point win in 2014.

Last night, Cruz won the county by just 8 points.