Attorney General Jeff Sessions is the second senior Trump official to have obscured the extent and nature of his contacts with Russia. In the wake of revelations that he failed to disclose meetings with the Russian ambassador, he recused himself Thursday from overseeing any investigation of Russian involvement in the 2016 election. His announcement was probably enough to placate a number of prominent Republicans who called for him to do that very thing. But demands from Democrats for Sessions to follow Michael Flynn's lead and resign will only grow louder now.

Throughout all this, however, we haven't heard much from supporters in the foreign policy community of a better relationship with Russia, particularly those with longstanding GOP ties. And it's time they spoke up. They should be the leading voices demanding a full and frank accounting of just what the Trump campaign was up to — because without it, a new Cold War is likely upon us, whether Trump wants one or not.

The most anodyne explanation of those contacts between Trump and Russia would look something like this: The Trump campaign, from its early days, decided that if they won the presidency they would seek significantly better relations with Russia, so they made numerous contacts with Russian officials at every level in order to sound the Russians out about the possibilities for such a sea change.

This would not necessarily have been inappropriate in any way. It is entirely normal for American presidential campaigns to have contact with foreign leaders and their representatives, and the Russians themselves have said they reached out to both the Trump and Clinton teams during the campaign, and that Trump's team was far more receptive to substantive discussions.

But in the context of evidence that Russia played dirty tricks to damage the Clinton campaign, any offers to Russia that the Trump team might have made during their discussions would look positively incendiary. So perhaps Flynn, and now Sessions, hid the extent of their contacts simply to avoid being caught up in a witch hunt. If they did so, they made serious errors in judgment — and must pay the consequences. But there is a big difference between being evasive about embarrassing facts and covering up a crime.

It could be worse, though, if the anodyne explanation is incorrect.

The most inflammatory possible explanations for the Trump campaign's contacts are that either Trump himself or high-placed members of his team were susceptible to Russian financial pressure or blackmail — or that the Trump campaign colluded with the Russians on dirty tricks to defeat Hillary Clinton. Either would clearly justify prosecutions and likely impeachment.

There is no evidence at this point to support such claims. But in this environment of near-hysteria, and in the absence of a full congressional investigation, absence of evidence is hardly proving exculpatory.

The Trump administration might not want such an investigation, though, for reasons having nothing to do with the substance of any discussions with Russian officials. Investigations inevitably metastasize, and draw attention away from an administration's substantive agenda. In today's hyper-partisan climate, it's even more likely that a GOP-led investigation that came up empty would simply be dismissed as part of a coverup.

Individual members of Congress, meanwhile, might support or oppose an investigation for reasons that have nothing to do with the substance of the issue. Opponents of rapprochement with Russia, for example, would have every reason to want to make continued pursuit of such a policy politically toxic.

Which is precisely why it is supporters of such a policy who should be taking the lead in calling for such an investigation.

The Trump administration could stonewall its way through this ongoing scandal, counting on rank partisanship to carry it through the worst. If there were genuinely no crimes committed, such a strategy might even succeed when and if Congress changes hands, and in the meantime the GOP have two years to pass their legislative agenda.

But until the air is clear, American policy towards Russia is badly tainted. Every move this administration makes is being interpreted through the lens of the most outlandish suppositions. In such a climate, the rational thing for the administration to do is abandon any plans for substantive improvement of relations. The Russian government is reportedly already operating on the assumption that Trump will not prove as friendly as hoped, both because of his own personal deficiencies and because of the widening impact of the scandal.

A congressional investigation could well prove a millstone around the administration's neck, and provide ample opportunity for Democratic grandstanding. But it's also the only way to rescue American foreign policy towards Russia from a widening gyre of increasingly fantastical speculation and innuendo.