The House now has a constitutional duty to impeach
Donald Trump is causing a constitutional crisis with his blanket refusal to respond to any subpoenas.
So what happens now? An impeachment inquiry in the House won't send him packing before Election Day 2020 because Senate Republicans won't convict him of impeachment.
So the practical political question is whether a House impeachment inquiry helps send him packing after Election Day. That seems unlikely.
Probably no more than a relative handful of Americans are still unsure of how they'll vote on Nov. 3, 2020. An impeachment is unlikely to reveal so many more revolting details about Trump that these swing voters would be swayed to vote against him, and their votes wouldn't make much of a difference anyway.
Besides, the inquiry probably wouldn't reveal much that's not already known, because House subpoenas will get tangled up in the courts for the remainder of Trump's term (even though courts give more deference to subpoenas in an impeachment inquiry).
Worse yet is the chance that an impeachment inquiry plays into Trump's hands by convincing some wavering voters that Democrats and the "deep state" are out to get Trump, thereby giving him more votes than he'd otherwise get.
Does this mean House Democrats should avoid taking the political risk of impeaching Trump? Not at all.
Another question needs to be considered -- not just the practical political effect on the 2020 election, but something more important over the long run.
It is whether an action designed to enforce our constitution is important for its own sake -- even if it goes nowhere, even if it's unpopular with many voters, even if it's politically risky.
Every child in America is supposed to learn about the constitution's basic principles of separation of powers, and checks and balances.