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In the 2008 Democratic presidential primary, the three leading candidates — Hillary Clinton, John Edwards and Barack Obama — spent months fighting over health care policy. That long debate helped to educate voters. It also helped the candidates and their aides better understand the thorny politics of health care, which in turn made it easier for Obama and Congress to pass a sweeping health care law after he became president.

In the 2016 Democratic primary, Bernie Sanders laid out a highly progressive set of policies, including a $15 minimum wage and Medicare for All. He didn’t win the nomination, but he did shape the Democratic Party’s agenda.

The 2020 campaign is now only a couple of weeks away from its first Democratic debates, on June 26 and 27, in Miami. So it’s the right time for candidates to begin rolling out their policy platforms.