(CNN) Tonight, after President Donald Trump delivers his State of the Union speech and former Georgia gubernatorial candidate Stacey Abrams deliver the official Democratic response to that speech, Bernie Sanders will have his say.

"For the third time, Sen. Bernie Sanders (I-Vt.) will deliver a response to President Donald Trump's State of the Union address Tuesday night," the press release sent to reporters announced Monday afternoon.

That is a very bad idea for Sanders.

Why? Simple. Because Sanders is a near-certain candidate for the Democratic presidential nomination in 2020. (He has yet to announce a candidacy but everyone expects he will.) But he has been -- and plans to remain -- an independent in the Senate, identifying himself as a democratic socialist, not a Democrat.

During the 2016 campaign, as Sanders was mounting a surprisingly competitive challenge to Hillary Clinton in the Democratic primary fight, there were whispers -- that turned into shouts by the end of that race -- that Sanders wasn't even a "real" Democrat, so how could he be allowed to run for the party's nomination?

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