Texas House District 40, which is anchored by the Rio Grande Valley town of Edinburg, encompasses one of the poorest areas in the state, with 42 percent of its residents living below the poverty line. The population is 94.9 percent Hispanic. More than half of its adults never graduated from high school. Not surprising to anyone who follows Texas politics, the district is also solidly blue. It has never elected a Republican when a Democrat was on the ballot, and 2010 was no different. In November, 76 percent of District 40 voters backed Democratic gubernatorial candidate Bill White over Republican incumbent Rick Perry. Those same voters also gave Democrat Aaron Peña, who ran unopposed, his fifth term in the Texas House. Though the election was a disaster for Democrats statewide, all seemed well in District 40.

Then came December 14, a day that will live in infamy, at least for Democrats in Texas. That afternoon, at a press conference at Republican party headquarters in Austin, Peña appeared, flanked by Perry, House Speaker Joe Straus, and Lieutenant Governor David Dewhurst, to make a cataclysmic announcement. He looked giddy as he stepped to the microphone, and so did the Republicans gathered around him. “I used to think Republicans had horns,” Peña said. “But I checked, and they don’t!” Though he had spent his whole career opposing them, Peña now declared that he felt more at home among Republicans. He was switching parties.

Peña’s defection, which happened at the same time Nederland state representative Allan Ritter decided to change parties, heralded a supermajority for Republicans by boosting their membership in the House to 101 lawmakers. No longer would the GOP have to fear upstart Democrats’ resorting to guerrilla tactics like that quorum-busting road trip to Oklahoma in 2003. Thanks to Peña and Ritter, the Republicans were a quorum.

But Peña’s conversion had even larger implications. As the first Hispanic member of the House to switch from Democrat to Republican, he represented the opening salvo in an epic struggle in Texas politics. With Hispanics expected to claim a majority of the Texas population by 2020, the continued dominance of the state Republican party depends on its ability to attract Hispanic politicians, who will in turn keep the party from losing touch with a growing constituency. Meanwhile, the Democrats have staked their best hope for a resurgence with the emerging Hispanic voting bloc. For years, observers have assumed that these demographic changes benefit Democrats, but Peña’s decision casts doubt on these assumptions. He himself has argued that Democrats have been taking for granted the support of the Hispanic community. Furthermore, many Hispanics adhere to values consistent with Republican principles. As Catholics, they are pro-life; as small-business owners, they loathe taxes.

Certainly the November election provided evidence that the Hispanic Republican has emerged as a viable political species. Texas elected two Hispanic Republican congressmen and six Hispanic Republican members of the Texas House. Buoyed by their success, Republicans began planning to use their advantage in this year’s redistricting to field more Hispanic candidates. And in Austin, many political observers extolled Peña as a prescient political strategist on the leading edge of a massive demographic shift. But was his partisan maneuver as canny as all this or was it just one more odd move by a quixotic politician who, back in District 40, now has no chance of winning reelection ever again?

I caught up with the 51-year-old Peña in February, over a plate of tacos at a restaurant in Edinburg. The evening had started on a promising note, as I accompanied him to the beautifully restored Edinburg Municipal Auditorium for the mayor’s state of the city speech. Local pols greeted Peña with abrazos and backslaps. Mayor Pro Tem Agustin “Gus” Garcia politely introduced Peña, betraying no indication that only recently he’d announced that he might run against him in 2012.

But as a local journalist interviewed Peña, a scowling man accompanied by his two young sons watched in angry silence. After the interview, he unloaded on Peña, who looked crestfallen. Pushing through the crowd, I introduced myself to Daniel Vasquez, who told me he had brought his sons so he could show them to Peña and castigate the lawmaker for failing to protect their education.

“I’m very angry,” Vasquez told me. “A lot of people are. We’re one hundred percent Democratic down here!” Waving his hand at Peña, he added, “He backstabbed us!”

The exchange darkened Peña’s mood: “What I said to him was ‘Give me a chance to win back your trust.’ He said no.”

As we walked out into the balmy night air, Peña seemed sincerely hurt. “I could have become a Buddhist and nobody would have said anything. I change parties and they go berserk!” he said with wonder.

His wonder may come in part from the fact that he has always staked out an independent path for himself as a politician. The personal has always seemed to matter to him more than the partisan, for better or for worse. He was the first major politician in the state to embrace blogging (you can find him at www.acapitolblog.com) and emerged as an avid user of Twitter (follow him at @aaronpena). Like most people in the Rio Grande Valley, he inherited his membership in the Democratic party. The son of a successful attorney in Edinburg, Peña volunteered for Hubert Humphrey at the age of nine. He remembers the thrill he felt as a student at the University of Texas in the late seventies when he heard Henry Cisneros speak.

But he worked outside the local party machine when he decided to become a candidate, which he now says planted the seeds of distrust. “I didn’t ask anyone’s permission to run,” he says. In fact, it was a highly personal decision, motivated by the tragic death, in 2001, of his sixteen-year-old son, John, from a drug overdose. According to Austin political consultant James Aldrete, who worked on Peña’s first election, John’s death defined his father’s campaign. “It became about making sure we had a drug abuse treatment center in the Valley,” Aldrete said.

Perhaps because of the intensely personal way he came into elected office, Peña relishes the role of the outsider, commenting frequently—on his blog, on Twitter, and to anyone who will listen—on the patrón system of South Texas, in which elections and government contracts are hopelessly intertwined. The Valley does not have a monopoly on dirty dealings, but it is an open secret that politiqueras are paid by candidates to deliver voters to the polls and assist them in casting their ballots. “It is an industry,” Peña told me. “Where I come from, people don’t have confidence in the elections.”

His long-simmering unhappiness flared up after the massive defeat that Republicans handed his party in November. Peña skewered the Democratic leadership for failing to engage Hispanic voters in South Texas. His comments prompted rumors that he might jump ship, and Peña once more felt besieged. “The professional left says, ‘You are a sellout,’” he told me. In early December, a reporter asked him if the speculation was true. Maybe, he replied. “It was a flippant remark that grew more serious,” he said, leading, pretty quickly, to his appearance at the December 14 press conference in Austin.

The response was swift and hateful. State senator Juan “Chuy” Hinojosa called upon him to resign. Blogs erupted with curses and rants about prior Peña flip-flops: his support of Republican Speaker Tom Craddick, his abandonment of the Hillary Clinton campaign for Obama, his shift in allegiance from the liberal-leaning Texas Trial Lawyers Association to its nemesis, Texans for Lawsuit Reform. Democrats felt betrayed and pointed to posts from Peña’s blog that made it hard to believe he truly felt at home across the aisle. During the contentious 2006 state Republican party convention, for instance, Peña had quoted state Republican chairwoman Tina Benkiser asserting, during a speech about immigration, that Texans are “in a war for our culture.” He blogged, “There is no subtlety here. No code words where the wink, wink and a choice phrase tells us that ‘THEY’ are different and results should follow. No folks, the chairman of the Texas Republican party is telling us that they are in a ‘war’ with half of the citizens of their state.” A subsequent post urged Hispanics to leave the convention rather than endure the insults.

What changed? The key to resolving the mystery may lie in Peña’s service on the House Redistricting Committee assignment. Not only did Hispanics contribute 65 percent of the growth in Texas in the past decade, they broke out of the barrio. Over the past ten years, the suburbs have become the fastest-growing areas in Texas, thanks largely to Hispanics. The Dallas–Fort Worth area is now home to more Hispanics than the Valley. Peña came to believe, he says, that the economic assimilation of Hispanics will lead many of them to the Republican camp. Months before his party switch, I spoke to him about the redistricting challenge. We talked about the data showing the growing dispersal of Hispanics, as well as the likelihood that Texas would earn four new congressmen. His take, offered long before rumors of his party switch, was this: “We could end up with three Hispanic Republicans: one in South Texas, or Austin to San Antonio; Dallas to Fort Worth; or Corpus Christi north to San Antonio. It could be a great opportunity to have three Hispanic Republicans.” This could be helped along by redistricting. As Republican strategists divide Texas into congressional and legislative districts, they’ll be aiming for “coalition districts” that pair conservative and Hispanic areas. This creates opportunities for Hispanic Republicans. Already, TLR, the Associated Republicans of Texas, and Hispanic Republicans of Texas, which was founded by George P. Bush, have begun generously backing Hispanic candidates.

This scenario carries with it two huge asterisks: First, how willing are Republican primary voters to back candidates with Hispanic surnames? Just last year they turned down railroad commissioner Victor Carrillo, a Perry appointee, for an unknown opponent, David Porter (though in November, two Hispanic Republicans won congressional races, Francisco Canseco and Bill Flores). Second, how will Hispanics respond if the Legislature passes bills that are viewed as hostile to them, such as the proposal that punishes an employer for hiring an illegal immigrant unless the job relates to housework?

And for Peña, these questions may be purely academic. The next election cycle won’t begin for another year, but his fate may be sealed by May 30, when the Legislature adjourns its regular session. Though he is pushing an ambitious agenda to clean up elections and to institute a guest worker program, by then he’ll have taken tough votes on legislation sure to be anathema to his constituents, such as giving police officers the right to pull over “suspected” illegal aliens. He has already voted for a voter ID bill condemned as racially motivated by Democrats, but he went against his new party on the House version of the budget, which includes deep cuts to public schools, nursing homes, and various social programs. What are the chances Peña can vote with Republicans and still survive another election cycle? “He’s walking dead,” one political observer told me.

But Peña’s fate could also hinge on whether the redistricting gods turn District 40 into one that is competitive for a Republican or whether his crusade for clean elections will earn him a political appointment. “I hope I’ll have a constructive influence on my new party,” he told me. “As a Democrat, I wasn’t allowed to express myself. I was half of an individual. When I became a Republican, I became a full individual.”