What lasting impact will President Donald Trump's undoing of large-scale Obama-era national policies have? According to Harvard law professor and former Obama appointee Cass Sunstein, there's still a reason to be hopeful if we consider the fact that Obama was able to enact impactful change in the first place.

On "Salon Talks," Cass Sunstein asserts that Obama played a crucial role in pushing politics toward beneficial change. "We had the most important social legislation since the 1960s. That's the Affordable Care Act. We had the most important financial regulation since the 1930s. That's Dodd-Frank. We had the most aggressive environmental movement probably ever in the sense of clean air, particulate matter, ozone, nitrogen oxide, and more, and that doesn't even mention climate."

Sunstein explores this concept, as well as many other social and political movements, in his new book "How Change Happens.".

Watch the video above to learn more about why Sunstein thinks Obama caused a sea change despite the Trump administration's dismantling of progressive policies. And check out the full episode for Sunstein's analysis of the #MeToo movement and how it changed people's expectations around gender and work.