The day after Ray Lopez advanced to the special election runoff for House District 125 last month, he called his three former Democratic opponents and asked for their support against Republican Fred Rangel.

It was not an unusual request for a runoff qualifier, but Lopez was not taking any chances — and neither are Texas Democrats.

In the weeks leading up to Tuesday's runoff for HD-125, the party has worked feverishly to avoid a repeat of last fall's race for another seat based in Bexar County, Senate District 19. Democrats lost that election under similar conditions: a special election runoff in a traditionally blue district where the Republican, aided by top party leaders, benefited from a fractured Democratic field in the first round. And it mattered greatly in the Senate, giving Republicans enough of a cushion so that they held on to their supermajority even after losing two seats in the November general election.

"For us at the [House Democratic Campaign Committee], the most important thing was to not allow what happened in SD-19 to happen in HD-125," said state Rep. Cesar Blanco of El Paso, who chairs the committee, acknowledging that Democrats "learned a hard lesson" in SD-19. "We wanted to make sure that right out of the gate, going into the runoff, there was a unified message."

The HDCC has helped Lopez, a former San Antonio City Council member, with fundraising, mail and polling. Meanwhile, the Texas Democratic Party has spent several thousand dollars on digital ads, assisted the Lopez campaign with voter targeting, placed party staff in the district, spearheaded a vote-by-mail program and sent get-out-the-vote texts.

In an interview, Lopez jokingly said that he has gotten "probably more guidance than anyone has ever needed."

Perhaps most notably, there has been a bigger outward display of Democratic unity in the HD-125 runoff than there was in the SD-19 runoff. In the first round of the SD-19 race, there was a bitter rift between two Democratic competitors, Pete Gallego and Roland Gutierrez, and Gutierrez did not endorse Gallego when he made it to the runoff.

This time around, Lopez entered the runoff with the backing of his former Democratic rivals, as well as every Democrat who represents Bexar County in Austin. They have made appearances at multiple events for him, and Texas Democratic Party Chairman Gilberto Hinojosa also has visited the district to stump for Lopez.

"The bottom line is, yes, I think they’re more motivated, more active," said Rangel's strategist, Matt Mackowiak, who also was Republican Pete Flores' consultant in the SD-19 race. "It remains to be seen whether they’re going to be successful or not."

Still, Mackowiak did not cede any enthusiasm, adding, "There’s a lot of excitement around this opportunity to flip this seat for the first time ever."

Rangel, a longtime party activist, easily finished first in the initial Feb. 12 contest for the seat, getting 38 percent of the vote to 20 percent for Lopez. Rangel was the only Republican on the ballot, while there were the three other Democrats in addition to Lopez.

The race was called after former state Rep. Justin Rodriguez, D-San Antonio, was appointed to the Bexar County Commissioners Court in early January.

In the lead-up to the Feb. 12 election, Rangel received the endorsements of Gov. Greg Abbott and U.S. Sen. John Cornyn, both of whom had also backed Flores. Asked Wednesday what spurred him to get involved in the HD-125 race, Cornyn did not hesitate to reference the outcome of the SD-19 contest.

“I would answer your question with two words: Pete Flores," Cornyn said. "I think that now-Sen. Flores ... was able to take advantage of the situation in that runoff to win in a district that was thought to be pretty blue, and I think that the Rangel race is perhaps another opportunity to do just that."

For Rangel's big-name backers, there is also another incentive: He would become the third Hispanic Republican in the House, a group that has seen its ranks diminished in recent election cycles. Cornyn said he continues "to believe that ought to be a priority for Republicans ... to recruit good candidates who reflect the diversity of their communities … and then take advantage that some of our Democratic friends in these special elections are asleep at the switch."

Beside Democrats appearing better organized this time, there are a few key differences between the HD-125 and SD-19 races. One is geography — SD-19 is anchored in San Antonio but spreads far south and west, encompassing vast rural swaths and hugging a significant portion of the Texas-Mexico border. HD-125, meanwhile, is almost entirely within city limits.

Both are solidly blue districts, though HD-125 is much more so than SD-19. In the U.S. Senate election last year, Democratic nominee Beto O'Rourke beat Republican incumbent Ted Cruz by 33 percentage points in HD-125 — and less than half that margin in SD-19.

And for Republicans, at least, one more seat in the 150-member House — even with their new slimmed-down majority — is not as valuable as the Senate pickup was. Several weeks after the SD-19 runoff, Flores' win proved crucial in preserving Lt. Gov. Dan Patrick's 19-member majority when two Republican senators, Konni Burton of Colleyville and Don Huffines of Dallas, lost their re-election bids.

Still, Republicans have mobilized for Tuesday. While Rangel does not have the campaign machinery that Patrick lent Flores in the SD-19 runoff, a number of GOP allies are working on his behalf. Abbott has recorded an ad with Rangel that is running on social media. The Texas Republican Party is sending emails and texts into the district, as well as recruiting volunteers for the last four days of the race. And other GOP groups, such as the Associated Republicans of Texas and the anti-abortion Texas Right to Life, are also advertising on social media and sending mail into the district.

In the runoff, Rangel has also picked up the support of another high-profile statewide official, Land Commissioner George P. Bush. The fellow Republican is set to host a fundraiser for the candidate Monday in San Antonio.

Campaign finance reports also indicate Lopez and his backers are not taking anything for granted. He significantly outraised Rangel from early February through March 2, $72,000 to $13,000. Lopez has since reported pulling in another $34,000. His biggest donor has been the Texas Trial Lawyers Association PAC, which has given $30,000.

As they sharpen their focus on the race in the homestretch, Democrats have found a galvanizing target in Rangel, who has openly supported President Donald Trump and gave an answer at a recent forum that appeared to defend Trump's now-repealed family separation policy at the border. Last week, Rangel held a rally at his San Antonio campaign headquarters with members of Latinos for Trump, a national group that works to build Hispanic support for the president.

Lopez's campaign seizes on the Trump affiliation in a new, attention-grabbing mailer that warns that Rangel "proudly supports Trump and would support extreme Republican policies at the State Capitol." It also features a more general plea, urging voters to "stop Trump Republicans by voting Democrat" on Tuesday.

If early voting numbers are any indication, the runoff is drawing more interest than the first election. After Thursday — the fourth day of early voting for the runoff — more people had cast ballots than they did during the two-week period leading up to the Feb. 12 contest.

Lopez acknowledged that, for Republicans, the race "probably is critical for them from a messaging perspective." But he also warned that they should not underestimate how seriously Democrats are taking it.

"We want to win," he said. "We want to win it big and let people know the Democratic Party is alive and well."