Pre-existing support base who don't demand policy action because they're fans, not constituents. He's been dabbling* with a rightwing anti-capitalist critique for awhile now, and Hawley et al. are signaling that's the new hustle for the party. He's ideologically malleable but rhetorically straight-forward. And he came up in conventional media so he may get more leeway initially from his gutless former colleagues.

Though that obviously depends on whether the GOP discards Trump as a model. A bigger, wider Dem win would have convinced me they'd maybe play it straight next time with a conventional politician like Cotton or Hawley. Somebody with a shot but who won't scandalize the donor class. Maybe Dan Crenshaw splits the difference? But I doubt their conclusion from 2020 will be that Trump failed, so Carlson seems like the best bet if they go looking for the next Trump. Though I guess "the field" is an equally good guess if I believe this. After all, if we did this in November 2012 I doubt anybody would have named Trump.

*struggling with verb choice there because it's not been consistent. that's partly because there's no such thing as a coherent rightwing anti-capitalism and partly because he's just trying on hats. so... dabbling.