Trump Jr. and his girlfriend, former Fox News host and attorney Kimberly Guilfoyle, joined Cruz for an afternoon rally in the town of Wichita Falls, roughly two hours outside of Dallas, and will join another rally in the evening with the senator in the town of Conroe, north of Houston.
Heaping praise on Cruz as a close ally of the president, Trump Jr. said the Texas senator "put aside any of those differences," from the 2016 campaign and has worked closely with his father.
"He's fought alongside of my father ever since, on every major vote. For every policy piece, for everything," Trump Jr. told the crowd in Wichita Falls. "He put aside any of those differences and he did what's right for you, because that's his job and he's doing it."
Trump Jr. also laid out the stakes for the 2018 midterm elections, where Republican control of both the U.S. House and Senate are at stake.
"You think you've seen dysfunction in D.C. recently?" Trump Jr. asked, "You ain’t seen nothing yet if you give Nancy Pelosi the House of Representatives, if you give Chuck Schumer the Senate. Let that be your motivation."
Seeming to put aside his past feud with President Trump, Cruz thanked both Trump Jr. and President Trump for their "steadfastness" in the face of "grief and attacks and nastiness" from Democrats.
"You endure a lot of grief, you endure a lot of attacks, you endure a lot of nastiness, and your father endures even more grief and attacks and nastiness, and let me thank you for your steadfastness and his steadfastness fighting for the country and ignoring the hatred on the other side," Cruz said.
Cruz also thanked Trump Jr. and Guilfoyle for making the trip to Texas, and the work they've done this cycle to turn out GOP voters in key races.
"Don and Kimberly they have been flying all over the country helping turn people out, helping raise money, helping hold on and grow our Republican majorities in the House, our Republican majorities in the Senate, because the stakes ... they ain't never been higher than they are right now."
The visit from the eldest Trump son marks the continuation of a thaw in the frosty relationship between Donald Trump and Ted Cruz, whose war of wards devolved into name-calling and salacious accusations throughout the 2016 Republican presidential primary.
"As far as Ted Cruz, he's one of the greatest liars and biggest liars I've ever known," Trump said of the Texas Senator in a March 2016 interview on This Week with George Stephanopolous, "He lies about so much. He lies about things that he shouldn't be lying about. He lies about things that don't matter."
"This man is a pathological liar," Cruz said of Trump in a May 2016 press conference, "He doesn’t know the difference between truth and lies. He lies practically every word that comes out of his mouth."
But with the GOP majority in the U.S. Senate at risk this year, and Cruz facing a spirited challenge from Democratic Rep. Beto O'Rourke, Trump and his allies are going all in for Cruz in the closing weeks of the campaign.
While a date for the rally has not yet been announced, President Trump announced on Twitter in late August that he will "be doing a major rally for Senator Ted Cruz in October," adding that he is "picking the biggest stadium in Texas we can find," to gin up support for his former rival.
At a campaign rally in Tennessee earlier this week, Trump gave a personal shout-out to Cruz and sounded optimistic about the senator's re-election chances.
"We love Texas. And Ted Cruz is starting to do really well in Texas now," Trump told the crowd in Johnson City, "He is a friend of mine. He's doing really well. He's going to win by a lot."
Trump Jr.'s visit also precedes an anticipated campaign appearance from Vice President Mike Pence, who is set to appear with Cruz at an event in Dallas on Monday, according to the Dallas Morning News.
While in Dallas, Pence will also campaign with GOP Rep. Pete Sessions, whose suburban congressional district is one in a host of Texas races Democrats are targeting this cycle in their quest to retake the U.S. House.
Sessions, the chairman of the House Rules Committee, is facing Democrat Collin Allred, a former NFL player and civil rights attorney, in the general election for the congressional seat he has held since the district was created in 2003. The district backed both John McCain and Mitt Romney by double-digits in the 2008 and 2012 presidential elections but was won narrowly by Hillary Clinton in 2016.
Wednesday's appearance also highlights the presence of Trump Jr., a dogged defender of his father and the administration's policies, on the campaign trail this midterm cycle. Last week Trump Jr. campaigned for Montana Republican Senate candidate Matt Rosendale and will head to North Carolina and Georgia next week to campaign for GOP candidates in tight races there, according to invitations obtained by McClatchy.
Trump Jr. has also been particularly vocal this week regarding the nomination of Judge Brett Kavanaugh to the U.S. Supreme Court, taking to Twitter Tuesday night to defend the president after he mocked the testimony of Dr. Christine Blasey Ford, who has accused Kavanaugh of sexual assault when the two were in high school, claims that the nominee has consistently denied.