Since last spring, Senate Democrats on the Foreign Relations Committee have been privately investigating Russian meddling in Eastern Europe without the assistance of committee Republicans.

Their efforts have been spearheaded by Sen. Ben Cardin (D-MD), the committee’s ranking member, and have involved outreach to foreign diplomats from countries that have been targeted by the Kremlin. Lawmakers have been in touch with dozens of European embassies for help gathering information, aides confirmed to The Daily Beast, in an attempt to chart how the Kremlin has used a sophisticated combination of propaganda and voter suppression to advance its global interests.

Sean Bartlett, a Democratic spokesman for the committee, called the report a “major” effort to expose how Vladimir Putin’s government has kept “the Russian public supportive of wars abroad, while distracted from the regime’s criminality and corruption at home, and how, over the past decade-plus, it has adapted that toolkit and taken it global.”

The report, he added, “describes how these efforts are led by the government’s security services and buttressed by state-owned enterprises, Kremlin-aligned oligarchs, and Russian criminal groups that have effectively been nationalized by the state.” It traces how the operations “emanate out of Russia in concentric geographic circles: they began in Russia, expanded to its periphery and former satellites, and then into the rest of Europe and eventually, the United States.”

It’s unclear when the report will be formally released to the public. A sources told The Daily Beast that Republicans were asked to be involved in its crafting. It’s unclear why they chose not to.

“We are aware that Sen. Cardin is developing a report on Russian efforts to interfere in European elections, but his staff has not yet shared it with us,” Micah Johnson, a spokesperson for Committee chairman Bob Corker (R-TN), told The Daily Beast.

There are numerous efforts already underway on Capitol Hill to investigate Russia’s election meddling, including in the House and Senate intelligence committees. The House effort has been marred by partisan tensions, and that committee’s chair promised to take a step back from the probe.

Sources close to the work being done by Senate Foreign Relations Committee Democrats say that they still hope Republicans will join their investigation. And others off the Hill say that the weightiness of the issue should encourage GOPers to be more involved.

“It will have a clarifying effect on policymaking, for the political class, if it lives up to its possibilities,” said a Republican affiliated with a Washington think tank, who is familiar with the committee’s efforts.

Unlike other Congressional probes looking at Russia, the Foreign Relations committee investigation doesn’t involve the United States’ 2016 election. Committee Democrats, instead, are taking a broad look at its malfeasance in Europe, including Russia’s history of cheating in the Olympic games, cyber attacks on former Soviet Bloc countries, and illegal annexation of Crimea.

“It’s not about Trump,” the Republican think tank fellow said. “But the impact will be: ‘Hey Mr. President, here’s a list of 55 sins of the Russians, and you’re kissing Putin’s ass—what’s the deal?”