Edward J. McCaffery is Robert C. Packard trustee chair in law and a professor of law, economics and political science at the University of Southern California. He is the author of "Fair Not Flat: How to Make the Tax System Better and Simpler" and founder of the People's Tax Page. The opinions expressed in this commentary are his own. View more opinion at CNN.

(CNN) Yes, now that the Democrats have taken control of the House of Representatives, they get to serve as committee chairs and that gives them the power of issuing subpoenas all by themselves. And, yes, Democrats can subpoena President Trump's tax returns, as they almost certainly will, and should -- there is much of potential interest in those returns, materially connected to Trump's possible conflicts of interest, foreign entanglements, and more.

Edward J. McCaffery

And, yes, Trump can oppose the subpoenas, and fight them in court, and it will be up to non-elected judges to decide the issue in the end. Meanwhile, our reality-TV-world of politics will breathlessly cover the twists and turns of the tale, as they already have begun to do.

But the Democrats got a much more important power on Election Day, one directly connected to the present and future well-being of all Americans. The US Constitution, in its so-called Origination Clause, provides that any law for raising revenue -- taxes -- must begin in the House. House Democrats, who won their majority largely by hewing to pocketbook issues such as healthcare and taxes, can do some real governance by using their power to tax to propose actual tax legislation.

What might this look like? Without getting into the weeds, there are two broad approaches to take. One, Democrats can propose a real, and fiscally responsible, middle class tax cut -- one that gives real benefits to working Americans and is paid for by asking for some payments from the wealthiest, who can now, like Jared Kushner , avoid all taxes.

Two, the Democrats can propose legislation that actually shuts down loopholes that the rich, like Kushner and his father-in-law, use to dodge paying taxes.

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