The race for Texas House Speaker grew more complicated when Rep. Ken Paxton threw his hat into a ring already occupied by current Speaker Rep. Joe Straus and Rep. Warren Chisum.

A conservative Republican from North Texas who’s affiliated himself with the tea party, Paxton told other Texas representatives in a letter that voting for his candidacy offers the best chance to enact a conservative agenda.

In a statement Paxton, R-McKinney, released Thursday morning, he promised to pass “true immigration reform,” a voter ID bill and to “reclaim our state sovereignty.”

“It’s not surprising to me,” said Sherri Greenberg, a lecturer at the LBJ School for Public Affairs and a former member of the Texas Legislature. “I have expected, ever since election night, that a Republican other than Rep. Chisum would get in the race.”

Paxton’s candidacy received a boost Friday, when Rep. Tan Parker, R-Flower Mound, announced he was withdrawing his support of Straus, R-San Antonio, and endorsing Paxton instead.

In response, 18 Republican Texas House committee chairmen wrote a letter endorsing Straus and said if Straus remained speaker, the House would pass legislation that is important to conservative activists.

“We have an ally on all these issues in Speaker Straus,” they wrote. “We have found him to be a staunch fiscal conservative in the model of President [Ronald] Reagan, whom he once served in Washington.”

Tensions in the race between Straus and Chisum, R-Pampa, erupted Wednesday when Chisum called on the current speaker to release everyone who had already pledged their support to him. Chisum claimed several Republican representatives that signed pledge cards for Straus after the speaker made significant donations to their campaigns created the appearance of impropriety.

“The exchange has the unfortunate effect of creating the perception that leaves members trading votes for campaign donations,” Chisum said in a statement. “Personally, I don’t think the members did that. But there is no denying the perception is there.”

Straus responded with a letter assailing Chisum’s claims of vote buying and said the challenge to his speakership was dividing the Texas House Republican caucus.

“Have you no shame?” Straus wrote. “At a time when we should be celebrating the historic Republican gains of the recent election and focusing on the business of the state, you have instead engaged in a campaign of distortions and attacks that have subjected the membership to a constant strain of negativity.”