There are many factors in Bernie Sanders’ defeat in Michigan on Tuesday, but one of them is likely that Sanders could not run on trade policy in 2020 as he did in 2016 — because President Donald Trump took it off the table.

In 2016, former Secretary of State Hillary Clinton was winning by 30 points in late Michigan polls before Sanders came from behind in what analyst Nate Silver said was “among the greatest polling errors in primary history.”

The exit polls revealed the secret of Sanders’s success: Democratic Party primary voters in Michigan opposed free trade by a 53% to 34% margin. Republican primary voters opposed free trade by an almost identical margin.

At the time, Sanders was campaigning against the Trans-Pacific Partnership (TPP). He had also long opposed the North American Free Trade Agreement (NAFTA). Clinton supported both. Michigan voters went with Sanders.

Trump’s positions on trade were similar to Sanders’s views — and he won Michigan in the general election, perhaps with the support of former Sanders voters. In office, he canceled TPP and replaced NAFTA with the U.S.-Mexico-Canada Agreement (USMCA). In that sense, Trump deprived Sanders of his winning platform by delivering it.

As a result, Sanders could no longer attract the same constituency in Michigan. Exit polls showed former Vice President Joe Biden defeated Sanders among union households.

It is an open question whether Michigan voters will reward Trump in November for fulfilling his promises on trade. But Sanders is clearly no longer as relevant.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News and the host of Breitbart News Sunday on Sirius XM Patriot on Sunday evenings from 7 p.m. to 10 p.m. ET (4 p.m. to 7 p.m. PT). He earned an A.B. in Social Studies and Environmental Science and Public Policy from Harvard College, and a J.D. from Harvard Law School. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.