Fmr. Secretary of State Hillary Clinton (D-NY) / Senator Tim Kaine (D-VA) ✓
Fmr. Governor Mitt Romney (R-MA) / Senator Rob Portman (R-OH)
The populists here would continue developing without Trump, and without the cult of personality he developed as president in the more turbulent late 2010s, he would be more easily forgotten. This would actually kind of be a problem for Romney in that a simple Trump endorsement wouldn't be enough to shore up the grassroots. He could do a decent job walking the tightrope between GOP factions and facing the weakened Democrats but it wouldn't be enough. Trump IOTL was just the right candidate at just the right time.