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The evolution of Trump and Romney's relationship, as told by their tweets

(CNN) Based on just their virtual love-fest Monday, you'd never know that President Donald Trump and Mitt Romney have spent years at each other's throats. Trump endorsed his former rival's run for a Senate seat Monday, and Romney was effusively thankful.

The last time the two had played nice on social media was way back in 2012, when Trump backed Romney for president. He even called Romney "fantastic" after his first debate with Barack Obama.

But as with most things on Twitter, the cordial moment was fleeting. Plus, a lot can happen in six years. Don't be surprised if some of these tweets show up in your "in case you missed it" feed Tuesday:

It seems like they patched things up after the election -- Trump was pleased with Romney's congratulatory call.

Maybe they worked things out -- or settled at being frenemies. Although Trump didn't end up picking Romney to serve as secretary of state, we'll always have this awkward photo.

President-elect Donald Trump and Mitt Romney dine at Jean Georges restaurant, November 29, 2016 in New York City.