Greg Sargent: How bad is the Republican cover-up on Trump and Russia? We may soon find out.

Just how far will congressional Republicans go to prevent a full accounting of Russian interference in our election and any possible Trump campaign conspiracy with it?

FILE - In this March 20, 2017 photo, House Intelligence Committee member Rep. Jim Himes, D-Conn., questions FBI Director James Comey and National Security Agency Director Michael Rogers on Capitol Hill in Washington, during the committee's hearing regarding allegations of Russian interference in the 2016 U.S. presidential election. For the third year in a row, the Fairfield County Democrat has proposed perennial legislation that commemorates the Feb. 12 birth date of Charles Darwin. The late British naturalist developed the scientific theory of evolution by natural selection. (AP Photo/Manuel Balce Ceneta)

As we head into 2018, one big, looming unknown is this: Just how far will congressional Republicans go to prevent a full accounting of Russian interference in our election and any possible Trump campaign conspiracy with it?

Certain House Republicans are already working to frustrate the House Intelligence Committee’s ongoing investigation. Do Democrats have any recourse? The answer is yes — but within limits.

In an interview with me, Rep. Jim Himes of Connecticut — the number two Democrat on the House intel committee — said that Democrats are seriously exploring the possibility of issuing a minority report that details the degree to which Republicans tried to impede a full investigation, should that end up happening. In this scenario, the public would at least have a clear sense of just how far Republicans went to protect Trump and his top officials from accountability.

“It’s in both the Democrats’ and the Republicans’ interests to...write a report based on a common set of facts,” Himes told me. “It would be a tragedy if the report has a minority section that says, ‘look, we wanted to talk to these two dozen witnesses and weren’t able to do so.‘”

In an important piece, The Post’s Karoun Demirjian reports that Rep. Devin Nunes, a Trump loyalist, may be wielding his influence as chairman of the intel committee to block critical lines of inquiry. Democrats have been alarmed by his tactics, especially the fact that despite his public recusal from the probe, he “never relinquished his sole, unchecked authority” to sign off on — or kill — efforts by Democrats to subpoena top Trump officials for more testimony:

“People familiar with the committee’s work estimated that Nunes’s effective veto cost Democrats dozens of requests for interviews and documents that were never sent out, despite repeated entreaties from the minority side.

“This includes requests for subpoenas to obtain additional testimony from key figures in the probe who Democrats say were not forthcoming enough in interviews — among them Attorney General Jeff Sessions and Trump’s son Donald Trump Jr. Democrats surmise they might have compelled them to return if not for Nunes’s resistance.”

In our interview, Rep. Himes confirmed that numerous Democratic requests to bring in witnesses haven’t been acted upon, though he did not confirm Nunes had killed those requests. He also confirmed that Democrats would like to bring in Sessions and Donald Jr. to ask “follow up questions.”

Democrats want to ask Don Jr. about a phone call he held with his father about his June 2016 meeting with the Russian lawyer, which he took in the expectation of receiving dirt on Hillary Clinton supplied by the Russian government. Don Jr. and his dad discussed this meeting just after news of it broke in July of 2017. When questioned about this call by committee Dems, he invoked attorney-client privilege. Dems want to subpoena Don Jr. to compel his testimony, which could shed light on what happened at that meeting and how far Trump has gone to prevent the truth about it from coming out.

It appears Nunes may have killed that effort. Meanwhile, Nunes’ investigative zeal is directed elsewhere: Politico recently reported that Nunes is quietly leading a group of House Republicans in an effort to build a case that senior Justice Department and FBI officials improperly handled the explosive “Steele dossier,” which describes links between Trump and Russia.

Trump this week called on the Justice Department to target FBI officials for unnamed acts, generally furthering the narrative — fed by Nunes and conservative media — that Special Counsel Robert Mueller’s Russia probe shows Trump is the victim of a corrupt “deep state” plot to reverse the election, and that the perpetrators of that plot should be prosecuted. Yet the New York Times has now reported that the probe came about when Trump adviser George Papadopoulos boasted to an Australian diplomat in May of 2016 that he’d learned Russia had dirt on Clinton in the form of thousands of emails, which the Australians then passed on to Americans, resulting in the original FBI investigation now run by Mueller.

Himes confirmed to me that Democrats want to call Don Jr. and Sessions back in to ask whether Papadoupoulos communicated to top campaign officials the existence of this Russian dirt on Clinton, and whether that is related to the June 2016 meeting to get said dirt from the Russian government. But it looks unlikely that Republicans will agree, and Himes said that if Republicans do end up frustrating a full inquiry more generally - and keep pushing the narrative of a deep state coup against Trump — Democrats may issue a minority report detailing what Republicans really did here.

“If the investigation gets wound up too quickly, the minority report would be largely about outstanding questions that were never examined,” Himes told me, though he stressed that he hopes this does not happen.

To be clear, this really might not happen: It’s possible Republicans will allow the inquiry to unfold, and/or that the full truth is not that damning to Trump and his associates. There might not be any cover up. Indeed, Republicans have protested that the Democratic requests for additional testimony are frivolous. But as Susan Hennessey and Benjamin Wittes point out on foreignpolicy.com, we can empirically evaluate whether Republicans are — or aren’t — making a good-faith effort to interview all the witnesses necessary to establish the full truth about Russian interference and possible conspiracy with it. So far, there is reason for concern that they aren’t.

And if they do not, a minority report might reveal this in full detail. (Meanwhile, the Mueller probe could reveal some of what Republicans did not want revealed.) Republicans may be able to prevent the full truth from coming out, but they cannot prevent the full truth about their own efforts to frustrate an accounting from seeing the light of day. At which point, the Democrats’ recourse will be political — to further the cause of accountability, they will need to win the House in 2018.

* DEMS MUST HOLD THE LINE ON ‘DREAMERS’: Trump recently tweeted that there will be no solution for the “dreamers” without money for his silly wall. The Post notes:

“Congressional Democrats have expressed openness to finding additional funding for border security but have ruled out funding the wall along the U.S.-Mexico border that Trump promised during his presidential campaign...Democrats are under intense pressure from Hispanic lawmakers and liberal activists to reject any government funding deal that does not resolve the DACA issue. Already, Democratic senators have helped pass multiple funding deals that did not include DACA protections, including one in December.”

My sense is that the most likely outcome is some kind of funding for fencing repair that Trump can falsely claim is a big victory for his wall. Dems cannot buckle here.

* GOP CHASING ITS OWN TAIL ON OBAMACARE: Politico reports that Republicans are deeply divided over whether to try again to repeal the Affordable Care Act:

“GOP leaders on Capitol Hill don’t want a repeat of last year’s Obamacare fumble: They spent precious time on a failed attempt to repeal the health care law every member of the GOP was presumed to hate. But they also don’t want to take repeal off the table, which would provoke conservatives who are still determined to undo Obamacare.”

The real question will be whether Republicans agree to act constructively in shoring up the law (crazy idea, I know). They might — if only because they now own the health system’s problems.