Timeline of Obama probe of alleged Trump-Russia ties

Editor's note: The following is an overview of events that led up to President Trump's controversial claim that the Obama administration was surveilling his campaign and its headquarters during the 2016 election campaign.

2016

June: The Foreign Intelligence Surveillance Court denies a FISA request by the Obama administration to monitor the communications of presidential candidate Donald Trump and some of his campaign advisers, according to BBC News and Heat Street.

July 25: The FBI announces it is investigating the hack of the Democratic National Committee, revealing the party's effort to ensure Hillary Clinton wins. The Daily Beast reports the FBI suspects Russian government hackers are responsible.

July 27: Trump is accused of inviting Russia to intervene in the election when he jokes about Hillary Clinton's missing emails and the WikiLeaks release of DNC emails, telling reporters: “Russia, if you’re listening, I hope you’re able to find the 30,000 e-mails that are missing.”

October: Hillary Clinton's campaign accuses Trump and the Russians of being the source of John Podesta's hacked emails, which are released by WikiLeaks.

Oct. 15: The FISA court grants an Obama administration request, focusing this time on surveilling a computer server in Trump Tower that allegedly would document Trump campaign links to Russian banks, according to Heat Street. The administration finds no evidence but continues the wiretaps, citing national security.

2017

Jan. 6: The director of national intelligence releases a declassified report that concludes Russian President Vladimir Putin had ordered an influence campaign to "undermine faith in the U.S. democratic process," damage Hillary Clinton’s election prospects and bolster Trump's, McClatchy reports. The campaign included the hacking of top Democrats’ emails and fake news distributed by Russian sources, the DNI report claims.

Jan. 10: Buzzfeed and CNN report a purported intelligence “dossier” claiming the Russians had regular contact with the Trump administration, but the document is quickly debunked as fraudulent.

Jan. 12: The New York Times reports the Obama administration has expanded the power of the National Security Agency to share globally intercepted personal communications with the government’s 16 other intelligence agencies before applying privacy protections.

Jan. 20: The New York Times reports the FBI, CIA, NSA and the Treasury Department are monitoring several associates of the Trump campaign suspected of Russian ties.

February: Reports surface that the FBI, in its probe of Russia-Trump campaign ties, intercepted a conversation in 2016 between Michael Flynn, when he was a private citizen, and Russian Ambassador Sergey Kislyak. Appointed by Trump as national security adviser, Flynn resigns for misleading Vice President Pence about the conversation, apparently denying he had discussed Obama's new sanctions on Russia amid a contrary claim by acting Attorney General Sally Yates, an Obama holdover, who cited an FBI transcript of the intercepted call.

Feb. 14: The New York Times reports members of Trump’s 2016 presidential campaign and other Trump associates had repeated contacts with senior Russian intelligence officials in the year before the election, citing four current and former American officials. The Trump campaign insists there is no evidence of any such coordination.

March 2: Attorney General Jeff Sessions recuses himself from any investigation into alleged Trump campaign collusion with Russia after the Washington Post reports he had contact twice with the Russian ambassador during the campaign in his role as a U.S. senator. Democrats contend the revelation contradicts his testimony at his confirmation hearings, but Sessions argues he was responding to a specific question about a breaking CNN article and understood it pertained only to his capacity as a campaign surrogate.

March 1: The New York Times reports the Obama White House "rushed to preserve" intelligence related to alleged Russian links with the Trump campaign.

March 4: Trump tweets: “How low has President Obama gone to tapp [sic] my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!”

March 5: White House press secretary Sean Spicer says in a statement, "Reports concerning potentially politically motivated investigations ahead of the 2016 election are very troubling.”

March 5: Former director of national intelligence James Clapper, who served President Obama from 2010 to 2017, denies Trump's wiretap claim on NBC's "Meet The Press" but also says that, to his knowledge, there was "no evidence" of collusion between the Russians and the Trump campaign.