(CNN) -- Thousands marched in Washington this weekend to call for action to counter climate change. With organizers estimating 35,000 people filling the National Mall, the Forward on Climate Change march was said to be the biggest demonstration thus far in support of this issue. "While they were fighting for equality," the Rev. Lennox Yearwood told the crowd, comparing them to those who took part in the March on Washington for civil rights in 1963, "we are fighting for existence." The protesters have support from President Barack Obama, who announced that he wants to make climate change a major issue in his second term. During his inaugural and State of the Union addresses, the president did not shy away from this controversial subject. But persuading Congress to pass this kind of legislation will be extremely difficult.
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Thousands marched in Washington to seek action on climate change
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Julian Zelizer: President Obama called action on issue a priority in last week's speech
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Convincing Congress to pass a bill on climate change is a heavy lift, Zelizer says
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Zelizer: Grass-roots organizing will be crucial to passage of a bill
Climate change has too often been an issue that is @placeholder-focused rather than grass-roots focused.