AMERICAN democracy has suffered a grave assault—yet political leaders from its two main parties cannot agree on how or even whether to investigate. In a move that is both astonishing and without precedent the Office of the Director of National Intelligence (DNI) on January 6th issued a declassified version of a secret assessment earlier given to Barack Obama and Donald Trump. It found that the intelligence services of a foreign country hacked into the e-mail accounts and computers of senior officials involved in the 2016 presidential campaign, notably at the Democratic National Committee, and released much of that stolen data to the WikiLeaks anti-secrecy website. The same hostile power also gained access to computer systems of several state and local electoral boards (though not systems involved in vote tallying) and used an array of front organisations, television channels and social media “trolls” to feed disinformation and propaganda to American audiences, in a bid to influence the result of the election and “undermine the US-led liberal democratic order.” In language as blunt as it is startling, the assessment, written by the Central Intelligence Agency, Federal Bureau of Investigation and National Security Agency, declares that this crime is no whodunnit. Though the declassified report does not make public its sources or supporting evidence, it declares the “high confidence” of American spy chiefs that they know the culprit. It finds that: “Russian President Vladimir Putin ordered an influence campaign… to undermine public faith in the US democratic process, denigrate Secretary Clinton, and harm her electability and potential presidency. We further assess Putin and the Russian Government developed a clear preference for President-elect Trump.”

This saga is shocking not because there is hard evidence that Russia succeeded in swaying the election results, though leaks from government officials to the Washington Post reported on January 5th that American spooks picked up gleeful communications among senior Russian figures celebrating Mr Trump’s win. The saga is so alarming because political leaders and the two parties have failed to unite in defence of their country.

Mr Trump’s reaction has been the most troubling. To him the hacking of the DNC and such figures as John Podesta, the chairman of the Clinton presidential campaign, is not so much a whodunnit as a “who cares”? In a long string of scornful tweets over many days he has cast doubt on American intelligence agencies, suggesting that they are too incompetent to know whether Russia is to blame (he mentioned their failure to find Iraqi weapons of mass destruction more than once). In an interview with the New York Times, shortly before being briefed on the DNI’s assessment, Mr Trump called the hacking probe “a political witch hunt” against him. He has urged America to “move on” rather than impose sanctions on Russia and in a statement after his briefing endeavoured to divert opinion away from Moscow. “Russia, China, other countries, outside groups and people are consistently trying to break through the cyber infrastructure of our governmental institutions, businesses and organizations,” Mr Trump said, promising that as president he would appoint a team to come up with a plan to combat cyber-attacks, whose details would necessarily remain secret to avoid helping foes.

Republicans and Democrats in Congress have mostly refrained from trash-talking American intelligence agencies, but otherwise struggled to present a united front. Perhaps the best way to understand this confusing situation is to take a leaf from the world of criminal justice. When seeking to prove a crime, cops and prosecutors know that they must weigh three key elements.

The first involves proving that a suspect had the means to commit a crime. That is not a controversial question in this case. Hacking is all too common, and many countries have been credibly accused of carrying out cyber-spying.

The second element in a criminal prosecution involves opportunity. This is the point that unites Mr Trump with Republicans in Congress. The president-elect and his future colleagues on Capitol Hill may disagree on whether Russia is behind the hacking, with such party leaders as Paul Ryan, the Speaker of the House of Representatives, saying that it is clear that Russia is to blame, and denouncing “any outside interference in our elections.”

But when it comes to explaining how hackers were able to steal e-mails with such ease, Mr Trump and senior Republicans have been happy to blame Democrats for allowing themselves to become victims.

To buttress that criticism Mr Trump has quoted the Australian founder of WikiLeaks, Julian Assange. One Trump Tweet declared: “Julian Assange said ‘a 14 year old could have hacked Podesta’— why was DNC so careless? Also said Russians did not give him the info!”

The chairman of the House foreign affairs committee, Representative Ed Royce of California, joined many congressional colleagues in a formulation of sinuous elegance. In a statement Mr Royce condemned Russia for hacking the election, but then pivoted and blamed a weak Mr Obama for creating that opportunity for mischief.

“This report confirms what we already know: Vladimir Putin’s acts of aggression pose serious threats to vital US interests. The Obama administration’s response to Putin’s propaganda machine was weak and ineffective in Eastern Europe, and now we’re paying the price here at home” Mr Royce declared, adding for good measure that the report found no evidence that “Russian meddling impacted our voting and tallying process in any way. Donald Trump won.”

But it is the third key element of a criminal prosecution that really divides the political classes: motive. All the rowing and squabbling about who did what among Republicans and between Republicans and Democrats boils down to this: lots of powerful figures in American politics cannot bear to contemplate a much more painful question, namely, why the hacking was carried out.

The DNI’s report does not mince words. It finds that the motive of the Russian government was to help Mr Trump win. The declassified report says: “Putin most likely wanted to discredit Secretary Clinton because he has publicly blamed her since 2011 for inciting mass protests against his regime in late 2011 and early 2012, and because he holds a grudge for comments he almost certainly saw as disparaging him.”

In contrast, the DNI report finds, Mr Putin publicly praised Mr Trump’s willingness to work with Russia and “pro-Kremlin figures spoke highly about what they saw as his Russia-friendly positions on Syria and Ukraine. Putin publicly contrasted the President-elect’s approach to Russia with Secretary Clinton’s ‘aggressive rhetoric’.”

There is more. Official Washington has seethed for months with rumours about various forms of leverage that Russia or Russian interests might have over Mr Trump. The DNI report does not shed any light directly on that question. But it does include the following striking paragraph: “Putin has had many positive experiences working with Western political leaders whose business interests made them more disposed to deal with Russia, such as former Italian Prime Minister Silvio Berlusconi and former German Chancellor Gerhard Schroeder.”

Mr Trump can hardly deny that he has called for closer and friendlier links with Russia. He has repeatedly praised Mr Putin as smart and strong. In July 2016 he publicly expressed hopes that Russian intelligence agencies had hacked into Mrs Clinton’s private e-mail server and encouraged them to publish what they found.

But for other Republicans, the idea that a hostile Russia thinks of the Republican president-elect as an ally is too much to bear. So that motive cannot be confronted head-on. Mr Ryan’s statement after the publication of the DNI report sidesteps the question of whether Russia might have wanted Mr Trump to win. Instead it seems to question the motives of those drawing attention to that claim, saying: “We cannot allow partisans to exploit this report in an attempt to delegitimise the president-elect’s victory. Donald Trump won this election fair and square because he heard the voices of Americans who felt forgotten.”

Mr Ryan and other Republican leaders have every incentive to want this story to go away, and stop casting a shadow on the inauguration of Mr Trump on January 20th. Given the Republicans’ unified control of the White House and both chambers of Congress, do not expect very much from committee probes into the election hacking which have been announced.

This tawdry tale cannot be forgotten, though. In the weeks between his election victory and taking office Mr Trump has chosen to tear down public trust in intelligence services he will soon lead, telling his supporters, in effect, not to believe the very federal bodies tasked with keeping the country safe. Follow the trail of means, opportunity and motive, and all evidence suggests that Mr Trump has carried out his own assault on America’s body politic.