A collision is coming, one that Democrats are giving themselves very little time or maneuvering room to avert.

On Friday, the Republican-led Senate returns to Washington and resumes its standoff with the House over the terms and timing of President Trump’s impeachment trial. On the very same day, the one-month countdown to the first presidential contest in Iowa begins.

After Iowa, the primary season will accelerate quickly. On March 3, Super Tuesday, states representing more than one-third of the U.S. population are set to vote. By the end of March, chances are that one of the 14 Democratic candidates now in the race will be close to nailing down the nomination, or the party will be headed toward a contested convention.

We have reached the point at which Democrats are going to have to make a choice: Do they want to squander precious days and weeks tilting against an impregnable Republican wall in the Senate, or do they want to make their strongest case for removing Trump from office to the people who might actually do it — the voters?

Until now, those impulses within the party were not working at cross-purposes. Two weeks ago, the House did its constitutional duty and, for the third time in U.S. history, impeached a president.

Along the way, the House Intelligence Committee uncovered a significant amount of evidence that the president had abused the power of his office by pressing Ukraine’s president to manufacture ammunition that Trump could use against a political opponent. Trump himself assured a second impeachment article, for obstruction of Congress, by stonewalling a legitimate inquiry into his actions.

But this is as far as the process is likely to go, given the political reality in the Senate. The Democrats have no leverage to force Majority Leader Mitch McConnell (R-Ky.) — who has already declared that he will not act impartially in the upcoming trial — to compel the testimony of witnesses the White House refused to provide to the House.

Democrats are left clinging to a thin hope that moderate Republican senators such as Lisa Murkowski (Alaska) and Susan Collins (Maine), who have both expressed reservations about the process, might put pressure on their leader. Or an even thinner one that Republicans might be jolted by new revelations at the margins of the scandal.

As it has since the proceedings began, Trump’s acquittal by the Senate appears certain. The impeachment drama has been all-consuming for the media and for Washington politicians, stoked constantly by the president’s rage-filled tweets. But average Americans are losing interest in a movie where they already know the ending.

Support for not only impeaching Trump but also for removing him from office grew significantly in the fall, after the first revelations of his July 25 phone call to Ukrainian President Volodymyr Zelensky. But it has not budged much since then, despite the witnesses who testified in the weeks leading up to the House’s historic vote. The public remains pretty much evenly divided on the subject, and Democratic presidential candidates say they rarely hear it brought up as they travel across the early primary states.

What people still want to know more about, however, is how the result of the next election could change their lives.

Multicandidate events in Iowa have been drawing large crowds of political window shoppers. Five Democratic contenders have already qualified for the next big one, a Jan. 14 debate in Des Moines.

But it is well within the realm of possibility that the three senators among them — Elizabeth Warren (Mass.), Bernie Sanders (I-Vt.) and Amy Klobuchar (Minn.) — will be back in Washington that day, sitting silently in the Senate chamber in their roles as impeachment jurors. That would leave the stage, as things stand so far, to former vice president Joe Biden and Pete Buttigieg, the now-former mayor of South Bend, Ind.

It’s fair to ask whether that matters, given there have already been a half-dozen Democratic debates.

But the weeks before the Iowa caucuses have a history of being fluid ones, and Sanders’s recent surge — including his eye-popping $34.5 million fundraising haul in the fourth quarter of 2019 — shows that Democratic voters are nowhere close to settled in their choices.

A number of the other Democratic candidates, including Biden, saw significant upticks in their totals as well. But Trump, by casting himself as the victim of his impeachment, fattened his campaign bank account by $46 million in the last quarter.

The impeachment imperative now, both on practical and substantive grounds, is for Democrats to move on. They are the ones who stand to suffer by delaying the inevitable.

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