Hughes, an attorney in Mineola, has raised $622,920 in campaign contributions — more than double Simpson's $259,129. He's also secured endorsements from the state's top Republican leaders, including Lt. Gov. Dan Patrick, Attorney General Ken Paxton and former Gov. Rick Perry.
But Simpson says he isn't worried.
"I feel good about the race," he said. "We're going to burn the candle at both ends and hope that I'm still left at the end ... [I am] dialing for dollars, kissing babies, running a big race."
Eltife has represented the Northeast Texas district that includes Tyler, Texarkana and Paris for 12 years. He styled himself as an "independent voice" and tended to become a swing vote on major pieces of conservative legislation, a point of frustration for some residents.
Pledging to hew to a more conservative line, both Hughes, 46, and Simpson, 54, announced their candidacies in June after Eltife confirmed he would not seek re-election. In December, the ticket expanded to include Army General James "Red" Brown and Mike Lee, a retired Navy hovercraft pilot.
Brown and Lee were knocked from the race during the March 1 primary. Lee garnered 9 percent of the vote while Brown trailed 13 votes behind Simpson, who finished with 21.3 percent. Hughes led the pack with 48 percent, a commanding lead, but not enough to win the GOP nomination for the seat outright. (The district is solidly Republican, so the GOP primary effectively determines who will win in November's general election.)
Hughes and his campaign did not return numerous requests for comment.
Heading into the May 24 runoff, both lawmakers have Tea Party backers and boast lengthy lists of endorsements.
Patrick created a two-minute video to make his pitch for Hughes, discussing conservative victories from the past legislative session and designating Hughes a "true conservative."
"Bryan has earned the respect and admiration of conservatives all across Texas for his work in the Texas House," Patrick said in the video. "He deserves to be elected based upon his outstanding work and his conservative leadership."
Simpson, the chief executive officer for Avinger Timber, said members of Republican leadership have backed Hughes because "they want someone who they can control."
"When has my opponent done anything that hasn't been politically safe?" Simpson said. "That's why the lieutenant governor said he would endorse my opponent: He wants a reliable rubber stamp for his agenda. And I'll support him when he's right, but I'm going to oppose him when he's wrong or when he wants to do what's right in the wrong way."
Simpson himself secured an endorsement from former Lt. Gov. Bill Ratliff, who preceded Eltife in the SD 1 seat. Simpson also received an endorsement from former candidate Lee immediately following the primary. Lee insists he is good friends with both candidates, but Simpson is "very honest and sincere."
"You may not agree with us 100 percent, but we will agree that something has to be done to change what's happening in Texas and America, and Bryan is just not going to do that," Lee said. "I love the guy, but Bryan has turned into the quintessential politician. He's turned into the guy down in Austin that we're trying to get rid of."
Lee said the district needs a candidate like Simpson who is willing to challenge authority, not Hughes who "is going to follow the money."
At least half of Hughes' campaign contributions came from Austin-based entities including Empower Texans PAC and the Texans for Education Reform PAC. The Empower Texans PAC, which tends to support far-right candidates, contributed $27,000 to Hughes' campaign and $2,000 to Simpson.
Simpson said these groups are supporting Hughes because they can control him, but Simpson insists he "can't be bought."
"This is a very conservative district, and I also believe it is a very independent district," Simpson said. "They want someone who not only was not going to expose tyranny on the left but tyranny on the right. They don't like being told what to do."