*Editor's note: This story has been updated throughout.
In a statement sent to The Texas Tribune, Johnson pointed out that, if elected, he would be the first speaker under the age of 45 since former House Speaker Price Daniel Jr. in 1973 and the first person of color to ever serve as speaker of the Texas House.
"I'm in it, and I'm in it to win it," Johnson told the Tribune.
Straus announced in October that he did not plan to run for re-election in 2018 — a move likely to shake up Texas politics for years. At the time, Johnson said that Texas would benefit from having a Democrat serve as House Speaker because “one-party rule has been the norm in Texas for far too long.”
Texas House members traditionally select a speaker on the first day of a legislative session. The next session will begin in January 2019, unless Gov. Greg Abbott calls a special session before then.
"I am deeply troubled by the far rightward shift in our state government and the excessive partisanship and the poor legislation this shift has spawned," Johnson said in a separate statement. "Texas has become a one-party state, and this has been to Texas’s detriment."
As a Democrat, Johnson would need bipartisan support to be elected speaker in the Republican-dominated House. Ahead of the next regular session, House Republicans agreed to select a speaker in their caucus and then vote as a bloc on the floor — a move that could completely cut out Democrats from picking the chamber’s next leader. Prior to the March 6 primaries, House Republicans pushed incumbents and candidates to sign a form promising to ultimately support the caucus pick. While Parker and King have signed the form, Zerwas has not.
Johnson, an attorney, is the vice chairman of the House Redistricting Committee and was recently chosen to serve as a delegate to the Democratic National Committee. He represents House District 100 in North Texas.
"What Texas needs is a strong, pro-growth, progressive leader presiding over the Texas House to act as a counterbalance to a far-right Governor and Lieutenant Governor. I am running for Speaker to help restore normalcy to Texas state politics," Johnson said.