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Hours after President Trump announced last year that the United States would exit the Paris climate deal, a broad group of governors, mayors and business executives declared that they would uphold the agreement anyway and continue tackling global warming on their own.

It was a striking move for a coalition of local leaders: Making a case to the rest of the world that they, and not the president, spoke for the nation on climate policy.

To date, however, that groundswell hasn’t been enough to counteract the effects of the Trump administration’s retreat on climate policy. Now, as many of those same local leaders and executives gather for a high-level conference in San Francisco this week, the group they created finds itself at a critical juncture, the moment when it shows whether or not it can rise to the task.

“Yeah, there’s pressure,” said Gov. Jerry Brown of California, one of the most visible faces of the movement, known as “We Are Still In.” State and local leaders “ are carrying the flag while the big powers, the national guys, are rather somnolent.”