PLANO, Texas (AP) — As it turned out, it would never be enough.

Sen. John Cornyn tried for more than a year to show Donald Trump and Texas Republicans that he and the president were on the same team.

LIVE RESULTS: Texas midterm primary runoffs

Cornyn posted a photo of himself reading Trump's "The Art of the Deal." He proposed legislation to rename a stretch of interstate in Trump's honor. Perhaps most glaringly, the Senate institutionalist who long supported the filibuster reversed his position in a failed effort to advance voting restrictions that are a priority for the president.

None of it worked. On Tuesday, Cornyn became the latest in a line of Republicans who lost their primaries after falling out of favor with a president with little tolerance for dissent and a seemingly insatiable appetite for retribution. The four-term senator lost by double digits to Texas Attorney General Ken Paxton, who Trump endorsed last week as "a true MAGA Warrior."

Cornyn, on the other hand, "was VERY disloyal to me," Trump wrote on social media.

READ MORE: Paxton makes his final pitch in the Texas Senate race against Cornyn, buoyed by Trump's endorsement

Trump's intervention in the Texas runoff came after weeks of successfully backing primary challengers in Indiana, Louisiana and Kentucky as revenge against incumbents who broke with his agenda.

Cornyn's attempt to avoid the same fate made even some of his supporters wince.

"You look at the positions he took to please the president and the groveling and whatever," said former Sen. Jeff Flake of Arizona, a Republican and Trump critic who didn't seek reelection during the president's first midterm in 2018. "It was rather painful to watch."

Trump took an uncommonly equanimous approach to Tuesday's results the following morning.

WATCH: A look at Trump's grip on the GOP as his critics are ousted in primaries

"Congratulations to Ken Paxton on such a tremendous win, and to John Cornyn for having run a strong and powerful race but, more importantly, having had a truly great career," he wrote on social media. "John will remain my friend for a long time to come, as we both watch Ken become a fantastic, common sense Senator, one who is respected by all."

Cornyn started early with ad touting pro-Trump voting record

Cornyn's loss wasn't for a lack of political gymnastics and astronomical campaign spending.

His campaign began running an advertisement last summer — part of an astounding nearly-$100-million air war by the senator and allied groups — with Cornyn looking into the camera and saying, "I voted with President Trump 99% of the time."

READ MORE: YOLO for GOP members? What unencumbered Republicans could mean for Trump's agenda

On Cornyn's campaign homepage, Trump and Cornyn stand side-by-side with thumbs pointed upward in an image aimed at projecting solidarity. Deeper in the website, the category titled "The Trump-Cornyn Record" notes the senator's role securing votes for Trump's signature 2017 tax cut bill.

Cornyn has also been championing provisions in Trump's signature tax-and-spending legislation to finance work on the U.S.-Mexico border wall.

The senator had dismissed the project as "naive" during Trump's 2016 campaign. But in January, he stood along a section of completed wall in Texas' Rio Grande Valley touting the measure's $11 billion for Texas contractors' work at "the direction of the president of the United States, to whom I am very grateful."

Cornyn's 2023 dismissal of Trump's return glares in background

Cornyn's praise for his party's leader and president were not unusual, but they clash with a statement Cornyn made in May 2023, when Trump was mounting his presidential comeback campaign.

"Trump's time has passed him by," he told reporters. "I don't think President Trump understands that when you run in a general election, you have to appeal to voters beyond your base."

Trump would go on to easily win the nomination and carry every battleground state in the general election.

Cornyn would hew closely to the president for the first 16 months of his second administration, hoping at the outside chance of his endorsement or to keeping him from weighing in at all.

But Trump did not forget the past slights.

"John Cornyn is a good man, and I worked well with him, but he was not supportive of me when times were tough," he wrote on social media while endorsing Paxton.

Smaller gestures, and one big one

Cornyn has playfully worked to promote Trump fandom, last year posting a picture on social media of himself thoughtfully peering into the pages of Trump's 1987 memoir and business advice book, "The Art of the Deal."

In a more obvious gesture, he proposed designating a section of a U.S. highway from the Texas Gulf Coast to Montana as "Interstate 47," to honor a 47th president with a well-documented love of naming things after himself. In a news release about the proposal, filed just over two weeks before Tuesday's runoff, Cornyn said it would be known as the "Trump Interstate."

The more tectonic shift occurred in March, after Trump had teased a possible endorsement of either Cornyn or Paxton in the runoff.

Paxton swiftly said he would consider dropping his candidacy if the Republican-controlled Senate lifted the filibuster and passed the SAVE America Act, a series of voting restrictions that Trump has described as an essential part of his agenda.

The following week, Cornyn wrote an op-ed in the New York Post — Trump's favorite hometown newspaper — backing away from his previous support of the filibuster. He vowed to "support whatever changes to Senate rules that may prove necessary" to get the bill "through the Senate and on the president's desk for his signature."

Flake watched with unease.

"I know John and his long-held positions on the filibuster and the Senate's institutions," he said. "No office is worth that."

Bedayn reported from San Antonio. Associated Press writer Mary Clare Jalonick in Washington contributed to this report.