As newly updated election results showed U.S. Sen. Ted Cruz’s victory was even tighter than first realized, Democratic-led voter registration groups are saying they’ve never felt closer to turning Texas into a true battleground.

Cruz’s margin of victory fell to just 214,921 votes, according to official results certified by Gov. Greg Abbott this week. That is about 5,000 votes closer than unofficial results showed last month.

Cruz won the race 50.9 to 48.3 percent — the closet U.S. Senate race in Texas since 1978.

While O’Rourke lost, groups like Battleground Texas say that margin of defeat is nearly four times closer than they thought was even possible and it has them itching to get to work on 2020.

“We can register that gap,” said Oscar Silva, executive director of Battleground Texas, a group that runs an aggressive registration program targeting potential Democratic voters.

The state saw twice that number of voters just registered between March and October, and Silva noted that every year 300,000 more Texas high school students come of age to register.

He said while many people suggest that 2018 was a one-year blip because of O’Rourke’s campaign, groups like Battleground Texas have been on the ground building an infrastructure that has lasting implications.

“That is sustainable,” he told the American Association of Political Consultants at a conference in Austin on Wednesday.

Battleground Texas said its data shows that, during early voting, nearly one out of every 25 voters under age 35 was registered by the group. Silva added that 69 percent of the people the group registered this year were voters of color, helping the electorate to begin to look more like the state’s overall minority-majority population.

Republicans have noticed their work too. In the summer, Gov. Greg Abbott’s campaign team used training sessions for volunteers to warn that Harris County and other big metro areas in Texas have been trending toward Democrats, thanks in part to the work of Battleground Texas volunteers.

Battleground Texas was first created in 2013 with the help of former campaign operatives who worked for former President Barack Obama. Their mission was to more aggressively register voters in Texas, a place that has a history of making it difficult to register to vote, Silva said.

He said the group made gains in voter registration despite Texas laws that he says “criminalizes voter registration.” In Texas, groups cannot help voters register unless they go through specific training in counties they want to work in. If someone wants to register voters in another of the 254 counties in the state, they must get retrained in that county. And the training sessions vary from county to county.

Silva said his group has more than 22,000 people who are certified to register people to vote in Texas. But Texas law requires all of those certifications to expire at the end of the cycle. All of those people must go through a new round of training to start registering voters again.

Texas saw record-shattering voter registration since 2014. Since then, Texas saw its voter rolls grow by almost 1.8 million voters. In the four years prior to 2014, Texas added just 756,000 voters.

The close margin of victory between Cruz and O’Rourke is something Cruz’s camp had been bracing for. Cruz chief strategist Jeff Roe told a conference of political consultants in Austin this week that in the closing weeks of the campaign, O’Rourke was surging.

“Waking up on Election Day, I knew it was going to be close,” Roe said.

He said the national environment was filled with stories about the Florida pipe-bomber sending packages to CNN and Democratic leaders. And then there were news accounts of the mass shooting at a synagogue in Pittsburgh. Roe said internal polling showed O’Rourke getting another half point closer for each of the final 10 days of the race.

“The last 10 days of the campaign was like nothing I’ve ever seen,” Roe said.

O’Rourke really surged along the I-35 corridor. In the counties from Laredo to the Oklahoma border, O’Rourke beat Cruz by more than 440,000 votes. Four years earlier, Republican U.S. Sen. John Cornyn easily carried that corridor by more than 300,000 votes. Over the last 12 days of the campaign, O’Rourke made at least 25 stops in counties along the corridor, compared to three for Cruz.