OPINION — An enduring Washington truth: When a politician uses multiple clauses in a sentence, the opening words are camouflage soon to be contradicted by what comes later.

Here are a few typical examples of this rhetorical shell game:

When a Democrat begins by saying, “While no one supports the rights of hunters and the Second Amendment more fervently than I do,” you can assume that the rest of the sentence will be an appeal for gun control.

Similar cynicism should be applied to a Republican declaring, “Throughout my career I have fought tirelessly to guarantee that all Americans have clean air and water, but…” The words after “but” will invariably call for more fracking, coal mining or oil drilling in national parks.

A prime example of this linguistic sleight of hand can be found in a revealing letter that 46 newly elected House Democrats sent to the party’s congressional leadership earlier this week. The key sentence deploys its final clause to undermine everything else:

“While we have a duty to exercise oversight over the Executive Branch, particularly when the Administration crosses legal lines or contravenes American values, we must prioritize action on topics such as the cost of healthcare and prescription drugs, our crumbling infrastructure, immigration, gun safety, the environment, and criminal justice reform.”

Despite its clotted written-by-committee prose, this is an important sentence to parse because it reveals a disconcerting naiveté in the expectations of the Class of 2018.

These fledgling House Democrats appear to be deliberately downplaying the importance of investigations into the excesses of the Trump administration. What that opening “While we…” clause suggests is that these incoming freshmen have no interest in focusing on the Russia investigation unless Robert Mueller proves that Donald Trump was secretly born in Moscow and is Vladimir Putin’s half-brother.

Instead, these youthful 46 House Democrats are brimming with enthusiasm to solve the problems of the world. This stance makes surface political sense following a Democratic electoral sweep that was powered by domestic issues like preserving Obamacare and the uneven benefits of the economic comeback.

Big heads?

But these Democratic freshmen have an unrealistic sense of their own importance in a political world dominated by Trump. It’s a common mistake to exaggerate the powers that come with a wave election: Nancy Pelosi’s elevation to House speaker after the 2006 election did not grant the Democrats the power to end the Iraq War any more than the 2010 Tea Party uprising allowed the GOP to repeal Obamacare.

In truth, the only legislative power the House Democrats will have in 2019 is the ability to say “no.”

With a comfortable House majority, the Democrats can veto the further dismantling of the Affordable Care Act, the construction of Donald Trump’s cherished border wall and the new trade treaty to replace NAFTA. But unless Mitch McConnell has a conversion experience rivaling St. Augustine’s, no House-initiated legislation will ever make it to the Senate floor.

Yet it is easy to envision the House Democrats, goaded by their newer members, spending months arguing over the nuances of a single-payer health plan and wrestling with legislation to overhaul immigration enforcement. Against the backdrop of dire warnings about the acceleration of global warming, far-reaching environmental legislation is likely to be approved by the new House.

Sure, this ambitious legislative agenda will give shaky Democratic incumbents useful bragging points for their 2020 reelection campaigns. And if a Democratic president is elected in 2020, the details of the House-passed legislation will be studied in the White House and dozens of congressional staffers will get administration jobs.

But that is about the extent of it.

Right now, the new House Democrats, in all their rainbow diversity, are the center of the political world — and feel justifiably proud about it. But what they fail to appreciate is how soon they will be overshadowed by the 2020 presidential race.

The issue fights that will determine the future of the Democratic Party will take place on televised debate stages rather than on the floor of the House. Presidential primary voters — and not legislators on Capitol Hill — will be the ones who will decide how far left the Democrats should go in 2020 and what will be the party’s vision for the post-Trump future.

Still dominant? Or dominating?

If Trump again runs for re-election, the election will be a referendum on his disruptive, discordant and dismaying presidency. No matter how proudly House Democrats talk about their prized bills that died in the Senate, Trump will dominate everything in a nationalized election.

That is why high-profile House hearings on the Trump administration are not only vital for reasserting congressional oversight, but they will also bring with them 2020 political benefits, if handled adroitly. The more voters know about the unseemly realities of Trump world, the better it will be for the Democrats in 2020.

Currently, investigative articles about the president, his family and his ethically challenged appointees fade from view without follow-ups on Capitol Hill. For example, Wednesday’s Washington Post story revealing that lobbyists for Saudi Arabia paid for 500 nights of hotel rooms at Trump-owned luxury properties in early 2017 cries out for a congressional hearing.

The Democratic freshman class must understand that the political formula that got them to Washington will not work again in 2020. Next time Trump will be on the ballot in a real rather than a symbolic way. Which is why investigating Trump, armed with subpoena power, should be the true priority of the new House rather than dismissed as a distraction on the road to legislating.  

Watch: Elissa Slotkin on Her Mission in Congress: Homeland Over Party, and ‘We Cannot Be in Endless Wars’