We finally have definitive evidence that the Obama administration engaged in clandestine operations against members of the Trump campaign. But the revelation that Stefan Halper was planted by the Obama intelligence community to gather information on the Trump team is only the tip of the iceberg in exposing the vast, unprecedented espionage operation.

Over the weekend, suspicions were confirmed that Stefan Halper — who has decades-long ties to the CIA and its British counterpart, MI6 — was a secret informant who gathered information on Trump campaign advisers Carter Page and George Papadopoulos.

Halper reportedly began to communicate with Page in mid-July 2016, which counters the timeline offered by former FBI Director James Comey, who claimed that the FBI’s Trump-Russia investigation began at the end of that month. He and Page continued to communicate well into President Trump’s tenure, which raises the possibility that the investigation did not conclude with the president’s election.

Halper is not a lone wolf

Halper did not initiate this operation of his own accord. He was a confidential informant; someone in the government had to be managing his role in the undercover operation. If congressional investigators can bring Halper in for an interview, they can ask him to expose the network behind the operation. At the very least, Halper obviously knows who he was reporting to.

It’s doubtful that Halper was the only human intelligence source

Halper was one of several individuals with known ties to the Obama administration and Hillary Clinton who approached Trump advisers.

Joseph Mifsud, who has claimed to be a member of the Clinton Foundation (and has donated to the organization), also approached Papadopoulos. He allegedly told the Trump adviser that Russia had “dirt” on Hillary Clinton. Notably, Mifsud has entirely disappeared from public reach.

Alexander Downer, whose tip (allegedly gathered from Papadopoulos’ drunk ramblings) supposedly prompted the Russia investigation, is also connected to the Clinton Foundation. As an Australian diplomat, he signed off on a $25 million dollar donation to the organization. He has refused to answer further questions about his role in prompting the investigation.

Don’t forget about the signals intelligence

The espionage operation against the Trump campaign and transition team also included electronic surveillance. We know this because Obama administration officials leaked the transcript of Gen. Michael Flynn’s phone call with former Russian ambassador Sergey Kislyak. The leak, which provided proof of a felony, also showed that signals intelligence was part of the comprehensive approach against the Trump team. We also know that both Paul Manafort and Carter Page were subject to wiretaps.

The Obama administration used national security letters (a secret subpoena that allows government officials to work around the FISA process, as they do not require approval from a judge) on at least four Trump campaign figures.

The cover-up: several Obama officials misled Congress about the investigation

Evidence continues to build that several high-ranking Obama administration officials — including former CIA Director John Brennan and former Director of National Intelligence James Clapper — may have misled Congress and the public about the origins of the Russia investigation.

Thanks to House Intelligence Committee Chairman Devin Nunes, we know that the Obama Department of Justice used a political opposition research document — the Trump-Russia dossier — as evidence to get a FISA warrant to spy on members of the Trump administration. We also know that no U.S. intelligence was used to back up any of the allegations in the dossier. Not surprisingly, not a single major allegation in the dossier has been proven.

Halper is at the bottom of the totem pole

As a confidential informant, Stefan Halper was not the mastermind of the operation, but a foot soldier in a sophisticated, unprecedented espionage campaign against a political rival. Surely, Obama loyalists will attempt to paint the Halper operation as a one-off. Yet it’s more than likely that the revelation of Halper’s spying is just the tip of the iceberg in uncovering one of the greatest political espionage scandals in American history.