Former failed presidential candidate Mitt Romney lamented Donald Trump’s upcoming announcement of his decision to quit the Paris Climate Agreement.

“Affirmation of the Paris Agreement is not only about the climate: It is also about America remaining the global leader,” Romney wrote on Twitter.

Romney’s message demonstrated what kind of president he might have been had he won his campaign against President Barack Obama in 2012.

He famously waffled on the issue during his campaign, eventually moving left on his position when he was considering another run for president.

“I’m one of those Republicans who thinks we are getting warmer and that we contribute to that,” he said during a speech in 2015.

Romney opposed Trump’s agenda during the 2016 Republican primary but tried to mend fences with the president after he succeeded where Romney failed.

“By the way, it’s not easy winning. I know that myself. He did something I tried to do and was unsuccessful in,” Romney said after a dinner with Trump at a New York restaurant in November. “He won the general election and he continues with a message of inclusion and bringing people together and his vision is something which obviously connected with the American people in a very powerful way.”

Romney was considered for a job in the Trump administration but was ultimately rejected, despite widespread support from the Republican establishment.