I'm worried that insurgent candidate like those in 'the squad' were only allowed to succeed as an olive branch to the left-populists for the purposes of maintaining a coherent anti-trump coalition.
The Republicans ran a reasonably clean primary in 2016, and got Trump, a demagogue completely dismissive of the party's interests, who catered to his base, and only helped the Republicans in circumstances of mutual interests. I don't think the party's leadership will be willing to risk something like that again, if the behavior of the Bush-era cabinet appointees he had is any indicator.