Idk, drumming up excitement can help people get to the polls to vote Cruz out. The Presidential race can help shore up the down ballot races. I'm hoping at least Walz shows up in MT. I would love to see them both but in particular he would appeal to people here and could boost Tester's numbers.
Trump won Texas by 5 1/2 points in 2020 - 52% to 46.5%. So this poll is consistent with the direction of Texas partisanship. Time and money spent to campaign Texas can be better used elsewhere.
Ted Cruz won in 2018 by like 2%. So getting people out to vote absolutely can make a difference. And you don't just turn a state overnight, it takes time and work.