A woman walks past a mural on a restaurant wall depicting US Presidential hopeful Donald Trump and Russian President Vladimir Putin greeting each other with a kiss in the Lithuanian capital Vilnius on May 13, 2016. Kestutis Girnius, associate professor of the Institute of International Relations and Political Science in Vilnius university, told AFP -This graffiti expresses the fear of some Lithuanians that Donald Trump is likely to kowtow to Vladimir Putin and be indifferent to Lithuanias security concerns. Trump has notoriously stated that Putin is a strong leader, and that NATO is obsolete and expensive. / AFP PHOTO / Petras MalukasPETRAS MALUKAS/AFP/Getty Images A woman walks past a mural depicting Donald Trump and Vladimir Putin kissing in Vilnius, Lithuania, in May. (Petras Malukas/Agence France-Presse via Getty Images)

The Wall Street Journal reports:

Republican and Democratic lawmakers say they plan to investigate Russian meddling in the 2016 presidential election, including the hacking of emails from Democratic political organizations and Hillary Clinton’s campaign staff.

But their efforts face a strong headwind from President-elect Donald Trump, who has continued to deny that there is proof of Russia’s involvement.

Reps. Eric Swalwell (D-Calif.) and Elijah Cummings (D-Md.) want to set up an independent commission, but the president would need to sign a bill calling for one. For now, despite public confirmation in October by intelligence officials that Russia engaged in hacking, President-elect Donald Trump says he does not believe the facts he has been given. Why? What information is he seeing that Congress is not?

Sen. Lindsey Graham (R-S.C.) is also interested in a probe, which could be done without Trump’s signature on legislation. “A spokesperson for Mr. Graham said he soon would join fellow GOP Sen. John McCain (R., Ariz.) in visiting Eastern European countries whose elections Russian hackers also are believed to have targeted,” the report says. “U.S. intelligence analysts have closely tracked those efforts, which included a proliferation of fake news sites, and now see the U.S. election hacking as part of a broader effort by Russia to interfere in the democratic process.”

Democrats should enthusiastically join with Graham and invite whomever they want as witnesses to testify, including Obama officials and ex-officials, Trump nominees and outside experts. Oversight is a core prerogative of Congress. In the case of national security, oversight is a key means by which the legislative branch exercises authority. Any attempts by the White House to quash an inquiry should be resisted. But why would Trump object? Don’t he and his nominees want to know — and want the public to know — the danger the West is facing? If not, we have bigger problems than one investigation.

Congress has the power of subpoena to call, for example, Democratic National Committee officials, forensic cyber-experts and gurus on hacking. What exactly did the Russians do and with whom did they coordinate? (One Russian official claims, without evidence, to have been in contact with the Trump people during the campaign; other stories have floated around claiming a cyber-connection between Moscow and Trump Tower.)

And while we are at it, each and every national security nominee needs to be asked in his or her confirmation hearing whether there is solid factual support to conclude that there was Russian meddling. Once everyone is operating from the same set of facts and with the same level of certainty, the president and Congress can go about formulating a policy to respond robustly, something the current administration has declined to do.

The president-elect chooses to operate in a fact-free zone where reality gets sliced and diced to fit his political ends and emotional needs. This was precisely why many voters did not trust him to serve as commander in chief. His vice president-elect insists that Trump has the “right” to voice opinions not grounded in facts. Actually, once in office, Trump has a higher obligation. He will not have the luxury of ignoring threats to the United States and our allies.

Regardless of Trump’s delusions, Congress has its own institutional obligations. Members of Congress take an oath to support and defend the Constitution of the United States against all enemies, foreign and domestic. Their willingness to investigate Russian attempts to subvert our democracy will test how seriously they take that oath.