The House Democrats have their work cut out for them. It’s become inescapably, ineluctably clear: The Trump administration isn’t going to comply with, acquiesce in or submit to congressional requests. Treasury Secretary Steven Mnuchin won’t turn over President Donald Trump’s tax returns. Attorney General William Barr won’t give Congress the unredacted Mueller report, contempt charge or no contempt charge. Commerce Secretary Wilbur Ross won’t testify any more about the census citizenship question. Former White House Counsel Don McGahn won’t produce, for now, either testimony or documents.

Trump himself, expansive as ever, has declared that his administration will resist “all” congressional subpoenas. If a third party, like Deutsche Bank, wants to comply with a House subpoena, the Trumps will sue the bank. No cooperation, nothing, nada.

So, what do Democrats do now? What strategies have the best chance of eliciting or compelling the testimony and documents they need for oversight, impeachment or both?

What strategies have the best chance of eliciting or compelling the testimony and documents they need for oversight, impeachment or both?

Plenty of experts are offering advice, with suggestions ranging from the straightforward to the baroque. But the laws governing this executive-legislative dispute aren’t black-and-white — which means that the other side is always going to have a plausible argument to present to a court, which, in turn, means that no magic legal slam dunks are available.

The Democrats have to face it: No technical trick is going to do the job. Their only route to success is via the muddy road laid out by master politician Abraham Lincoln: “Public sentiment is everything. With public sentiment, nothing can fail; without it nothing can succeed.”

The most straightforward procedural suggestion for addressing executive branch noncooperation is to subpoena documents and testimony and, if they aren’t produced, hold the responsible individuals in contempt of Congress. This, it turns out, is not such a great idea.

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For one thing, a congressional contempt citation like the one the House Judiciary Committee issued for Barr on Wednesday is evanescent. The process is almost comically inefficient, and requires the contempt citation to be eventually approved by the full House. The citation also expires at the end of the Congress that issued it. When a new Congress is seated, it can start again. In contrast, the executive branch marches on as an enterprise, legally speaking, from one presidency to the next. In a power struggle between president and Congress, this is a big advantage for the executive.

Then, there’s the enforcement dilemma. Criminal enforcement of a congressional contempt citation falls to the Justice Department. If you’re asking the current Department of Justice to move against executive branch officials, good luck to you. (This goes double for Barr himself, who of course leads the Justice Department.)

Alternatively, the House itself can file a civil suit, asking a court to enforce its citation — or otherwise order compliance. This is the proverbial long slog. Such proceedings are almost guaranteed to drag on for months or years.

The House can also impeach, or at least prepare to impeach, either Trump himself or his Senate-confirmed appointees. Some people favor this tactic because it’s a way to establish a clear legislative purpose — one a court would respect — to justify a demand for documents and testimony.

But this need for “legislative purpose” shows the larger problem for House Democrats seeking executive branch compliance: None of the laws involved are unambiguous enough to keep the dispute out of lengthy court proceedings.

This problem is demonstrated in the current fight over Trump’s tax returns. The Internal Revenue Code states the Treasury secretary “shall furnish ... any [tax] return” that the chairman of the House Ways and Means Committee requests. “Shall” leaves no wiggle room. Because of this provision, the tax return fight is the one, among all the current House v Trump clashes, in which Congress has the clearest statutory authority. Even here, however, where House Democrats can point to a specific statute, their authority is restricted by the requirement that it be used only for legitimate legislative purposes.

The House Ways and Means Committee's request for Trump’s tax returns has cited the legislative purpose of exercising oversight of IRS performance in auditing presidential tax information. It sounds reasonable. But, according to Mnuchin, Justice Department lawyers have asserted that the committee is actually singling out a particular president in ways that constitute presidential harassment rather than legitimate legislative inquiry. This, too, sounds reasonable.

The dispute is one that the parties can take all the way to the U.S. Supreme Court. Which, in case you’ve forgotten, now includes two of the 100 Trump-nominated judges who have been confirmed by the Senate.

In other areas in which Congress wants information, from the Mueller report to the census citizenship question, congressional authority rests less on specific statutes than on what we think of as bedrock constitutional principles of checks and balances. But the tectonic plates under the bedrock can shift. Trump’s “resist all subpoenas” position may sound outlandish — but by the time court pleadings are filed, it will be clothed in reasoned arguments about constitutional restraint and legislative overreach. Even if the judges aren’t predisposed toward the executive branch, the outcome of these cases is uncertain. No legal slam dunks are available.

There is yet another way to enforce a contempt citation, which is that the House can send its own officers to arrest and detain a noncompliant witness. But think about it. Picture the congressional sergeant-at-arms and his staff mounting a police operation against the armed security details that guard the attorney general or the Treasury secretary. Once again, good luck.

In short, as I said above, no clever technical trick will do the job. If Democrats try to fight the administration through procedural means alone, they’ll become mired in processes that will likely last well beyond the 2020 presidential election — which may be the Trump re-election. Instead, they have to do something harder: Mobilize public sentiment by refusing to “move on” from the Mueller report.

In judging the House Democrats’ options, it’s impossible not to think of Watergate, in which the House articles of impeachment against President Richard M. Nixon were substantially similar to the charges against Trump today: financial corruption, obstruction of justice, resisting lawful congressional subpoenas.

When we look back at Watergate, its course seems preordained. But it wasn’t until the spring and summer of 1974, two years after the break-in, that Republicans began deserting Nixon in droves. The collapse of the Republican wall that had shielded Nixon wasn’t due to any procedural coup by Democrats. Instead, the cause was sustained pressure from Democrats, judges and journalists, much-maligned, who refused to “move on” from the break-in and the sentencing of the Watergate burglars.

There are people who now urge that we move on from the Mueller report — which, whatever its other merits, won’t provide Democrats with leverage over the Trump administration. If they are to have their chance, it will lie in pursuing the highly contingent path of traditional politics.

That path is getting messier and more contingent by the day. More than 700 former Justice Department prosecutors have now signed their names to a statement asserting that the facts alleged in the Mueller report are, contrary to Barr’s statements, sufficient to support a charge of obstruction of justice. The head of the FBI has just testified to the Senate that he knows of no evidence of illegal surveillance of the Trump campaign.

The collapse of the Republican wall that had shielded Nixon wasn’t due to any procedural coup by Democrats. Instead, the cause was sustained pressure from Democrats, judges and journalists.

House Judiciary Committee Chairman Jerrold Nadler threatened Barr with contempt for not delivering the unredacted Mueller report, prompting the attorney general to counter-threaten to have Trump invoke executive privilege over the entire report — which he has now done. The New York Times has produced Trump’s tax information for a decade in which he evidently lost $100 million (you read that right) per year. Sen. Elizabeth Warren, D-Mass., who is running for president, called for impeachment on the Senate floor.

And there’s an election coming.

Remember Mao Zedong’s dictum: Political power flows out of the barrel of a gun. The clear-eyed brutality of this statement tore the veil off the fictions that govern much of normal political life. We probably won’t have to look down gun barrels any time soon, thank God. But Trump has done congressional Democrats the favor of reminding them that, at the very least, political power flows only out of Lincoln’s public sentiment.

If this sentiment can be mobilized or, in its meandering way, mobilizes itself, the Trump era will be over. If not, there will be — as another president once said — four more years. Nothing the Democrats can do in the way of court proceedings and parliamentary maneuvers is likely to stop it.