First-term Texas House Speaker Dennis Bonnen announced Tuesday he will not seek reelection to the lower chamber in 2020 — completing a stunning fall for the Angleton Republican who enjoyed near unanimous support in the House just months earlier.

“After much prayer, consultation, and thoughtful consideration with my family, it is clear that I can no longer seek re-election as State Representative of District 25, and subsequently, as Speaker of the House,” Bonnen said in a statement, which included a list of 43 House Republicans — a majority of the House GOP Caucus — that the speaker said "have made clear that it is in the best interest of both myself and the House to move on." (Bonnen's own brother, Greg Bonnen of Friendswood, was among those on the list.)

Bonnen’s political future was first called into question in late July, when hardline conservative activist Michael Quinn Sullivan, who heads the group Empower Texans, revealed that Sullivan, Bonnen and one of the speaker’s top allies had met at the Texas Capitol the month before. At that meeting, Sullivan alleged, Bonnen and state Rep. Dustin Burrows, R-Lubbock, suggested Empower Texans go after a list of 10 House Republicans and told Sullivan his group could have media access to the lower chamber in 2021. Bonnen also disparaged multiple Democrats, calling one “vile” and another “a piece of shit," and said his goal for the next legislative session is to make it the worst "in the history of the legislature for cities and counties."

A majority of members were at first unsure of what to think about the allegations, given that Sullivan was a longtime critic of House leadership and that their new speaker had overseen a legislative session that was hailed largely as a success. The allegation that Bonnen had planned to politically target members from his own party also seemed to contrast what he had announced the last day of the session: If an incumbent targeted another colleague, regardless of party, there would be consequences.

But that uncertainty disappeared for a lot of members last week, when Sullivan released his secret recording of that June 12 meeting that largely confirmed his allegations against the speaker. Bonnen, in response, said he did nothing criminally wrong — a nod to the criminal investigation into the matter by the Texas Rangers — and insisted the 150-member “House can finally move on.”

Since then, a growing number of Republicans — and Democrats, too — have called on the speaker to resign, arguing that the damage done by Bonnen is beyond repair. After the House GOP Caucus met Friday and released a statement condemning both Bonnen and Burrows for their remarks, the speaker’s biggest blow politically came Monday night, when five of the chamber’s most influential Republicans announced they could no longer support Bonnen for the post.

By Tuesday morning, more than 30 House Republicans had either called for the speaker’s resignation or pulled support for the speaker.

After the speaker's announcement Tuesday, Sullivan tweeted that Bonnen "could have behaved ethical" — but "instead chose lies, deceit, dishonor, and ruin."

"He has gone from 3rd constitutional officer in Texas to a cautionary tale," Sullivan wrote.

Bonnen's decision not to seek reelection means his seat in House District 25 will be open for the first time in over two decades. One Republican, emergency room nurse Rhonda Seth, was already running for the seat before Tuesday, aiming to take out Bonnen. The district in southeast Texas is solidly Republican.

With Bonnen's exit, members will be jockeying among one another to become the next speaker. That election won't happen until the next time the Legislature convenes, which is scheduled to happen in January 2021. In the meantime, if Bonnen remains in place until then, he can carry out typical interim duties, which include assigning issues for committees to study ahead of the next legislative session.

The race to replace Bonnen is coming ahead of a competitive election cycle for Republicans, who, after losing a dozen House seats to Democrats in 2018, are gearing up to hold onto their majority in the lower chamber. If Democrats were to flip nine seats and hold onto the dozen they picked up, they could be the party in power in the House and, consequentially, elect a member from their caucus to lead the lower chamber.

It's unclear what role — if any — Bonnen will play in 2020 in helping to hold onto the GOP seats. In July, before Sullivan's allegations surfaced, Bonnen announced he had infused a new political action committee with $3 million to support House Republicans running for reelection. Since the speaker became engulfed with the drama, though, some members have privately wondered whether Bonnen would be a help or hindrance to their fundraising efforts heading into the election cycle.

Democrats, for their part, cast Tuesday's news as "a victory for transparency and accountability."

"Texans are tired of politicians, like Republican Speaker Bonnen, who use backroom deals, cover-ups and outright lies to pursue power over everything," said state party Chair Gilberto Hinojosa in a statement. "Now more than ever, it is clear that only the election of Texas Democrats will return ... ethics and good governance to our great state.”

Patrick Svitek contributed reporting.