Editor's note: This story has been updated throughout.

HOUSTON — Democratic vice presidential candidate Tim Kaine used a speech Friday here to try to energize long-beleaguered Texas Democrats, reiterating his ticket's commitment to seeing the solidly Republican state become more competitive. 

“We take Texas very seriously — Hillary and I do," Kaine said while addressing state Democrats. The U.S. senator from Virginia added: "We look at what you’re doing … and we’re very, very proud of it. We can feel the spirit, the energy. We can see a state that has been red, a state moving in the best direction."

With polls suggesting a tighter-than-expected race in Texas, the Democratic nominee's campaign has been paying more attention than normal to the state, opening offices and dispatching surrogates. On Friday, Kaine made clear the moves were not for show, building on an optimistic outlook for state Democrats that he first shared during a trip last month to the Lone Star State. 

The Texas Tribune thanks its sponsors. Become one.

In Houston, Kaine encouraged Texas Democrats, who have been shut out of statewide office for more than two decades, to keep in mind a philosophy he shares with Clinton: "I'm the underdog until they call me the winner." 

"You Texas Democrats, you're the underdog ... but if you had that in your head — 'I'm the underdog until they call me the winner' — that's the discipline that you need to do the best work," he said. 

The Texas Republican party panned Kaine's bid for Lone Star support.

“The Hillary Clinton AstroTurf movement continues in Texas, as Tim Kaine made stops in Houston and Austin today. Despite the Clinton campaign’s claims to be taking Texas seriously, Democrats still have a message that isn’t resonating because their policies would hurt hard-working Texans," said Texas GOP spokesman Michael Joyce. "Instead of making a real impact, it seems that Texas Democrats with deep pockets have simply grown tired of sending money to the campaign, only to watch their money flow out-of-state.”

Like he did during his previous swing through Texas, Kaine pointed to his home state as an example of a once-red state that turned a bluer tint with hard work. "You're going to see the same thing happen in Texas that we saw" in Virginia, Kaine said.

Kaine, who was introduced by U.S. Rep. Sheila Jackson Lee, D-Houston, was met by a lively crowd at the rally, which was held at a local union headquarters that the campaign is using as its Houston outpost. At multiple points, the audience broke out in chants of "Si se puede!" — or, "Yes, we can," the campaign slogan of the current Democratic president, Barack Obama. 

The Texas Tribune thanks its sponsors. Become one.

Kaine's rally came three days before Clinton, the former secretary of state, and Republican rival Donald Trump are set to meet for their first debate. While Kaine warned that the race is volatile, he expressed confidence that she would prevail at the debate, which is being held at Hofstra University in New York. 

"When the spotlights are at the brightest and the pressure is the most intense, that’s when she brings her A+ game," Kaine said.

Kaine last visited the state in August, when he made a two-day trip to raise money in Austin, Dallas and Fort Worth. He also held a volunteer thank-you event in Austin, declaring there that the Democratic ticket is "very serious about Texas."

Since then, Clinton's campaign has further zeroed in on the state. It has sent surrogates for public events in Austin and Dallas, including Kaine's wife, Anne Holton, and Planned Parenthood CEO Cecile Richards. The campaign has also joined with the Democratic National Committee to open at least four offices in the state, with another one on the way Saturday in Dallas. 

Kaine's trip to Texas began Thursday evening, when he landed in Houston for a fundraiser whose hosts included Jackson Lee as well as Democratic megadonors Amber and Steve Mostyn. The event also featured a performance by Grammy Award-winning singer Michael Bolton. 

After the Houston rally Friday, Kaine headed to Austin for two more fundraisers. Shortly before Kaine took the stage in Houston, the Clinton campaign announced he would make a previously unscheduled stop in Texas' capital city: an appearance at a news conference hosted by Latino elected officials.

At that gathering, about 40 state representatives, county commissioners and other Hispanic Texas officials paired with Kaine to call for free college tuition and stress the importance of open borders and support for Hispanic small businesses. 

Switching between Spanish and English, Kaine said the country needs comprehensive immigration reform to create jobs, and blasted Trump's rhetoric calling for deporting millions of undocumented immigrants.

The Texas Tribune thanks its sponsors. Become one.

Texas officials said Clinton’s vision of building bridges instead of walls is vital for the Texas economy. El Paso County Judge Veronica Escobar said $90 billion worth of trade comes through El Paso’s ports every year, making Mexico the most important trading partner for Texas.

“Hillary Clinton understands the border,” Escobar said. “She doesn’t just understand the border but she appreciates the economic powerhouse that it is.”

Elena Mejia Lutz contributed to this report.

 Read our related coverage:

Disclosure: Planned Parenthood and Amber and Steve Mostyn have been financial supporters of The Texas Tribune. A complete list of Tribune donors and sponsors can be viewed here.

Get The Brief

Never miss a moment in Texas politics with our daily newsletter.