PHILADELPHIA — The FBI announced Monday that it is investigating how the hacking of thousands of Democratic National Committee e-mails occurred, saying ‘‘a compromise of this nature is something we take very seriously.’’
The Clinton and Trump campaigns have been fighting over whether Russia played a role in the release of the internal DNC messages, and whether the timing of the release was politically motivated.
The e-mail uproar has created an unwelcome distraction at the launch of the Democratic convention in Philadelphia, inflaming the rift between supporters of Hillary Clinton and primary rival Bernie Sanders just when the party was hoping to close it.
Clinton’s campaign, citing a cybersecurity firm hired to investigate the leak, blamed Russia for hacking the party’s computers and suggested the goal was to benefit Donald Trump’s campaign.
Trump dismissed that idea as laughable, tweeting: ‘‘The new joke in town is that Russia leaked the disastrous DNC e-mails.’’
Sanders supporters were irate that the e-mails confirmed their long-held suspicions the party had favored Clinton all along.
Democrats have known about the hack since April, when party officials discovered malicious software on their computers. The party publicly acknowledged the hack in June.
Party officials called in a cybersecurity firm, CrowdStrike, which found traces of at least two sophisticated hacking groups on the Democrats’ network, both with ties to the Russian government.
Those hacks vacuumed up at least a year’s worth of chats, e-mails, and research on Trump, according to a person knowledgeable about the breach who wasn’t authorized to discuss it publicly.
On Friday, the public got its first look at DNC e-mails when Wikileaks posted a cache of 19,000 internal communications, including some that suggested party officials had favored Clinton over rival Sanders during the primaries.
It wasn’t immediately clear how WikiLeaks got the e-mails, and WikiLeaks founder Julian Assange proudly told Democracy Now he would never tell.
Clinton’s campaign didn’t hesitate to make the connection to Russia, with campaign manager Robby Mook saying cyber experts believed ‘‘Russian state actors were feeding the e-mail to hackers for the purpose of helping Donald Trump.’’
Trump’s team went out of its way to dismiss the alleged Russian connection as outlandish. Trump senior policy adviser Paul Manafort called the Clinton campaign statements ‘‘pretty desperate’’ and ‘‘pretty absurd.’’
Whatever the source, the fallout from the leaked e-mails was swift and dramatic.
Democratic Party chairwoman Debbie Wasserman Schultz resigned over the weekend after Sanders’ campaign pounced on a number of leaked e-mails that they said showed that party officials had favored Clinton during the primaries.
The disclosure set off devoted Sanders supporters, who were already having a hard time moving past the bitter primary battles to embrace Clinton as the nominee.
The e-mail controversy has raised new questions about Trump’s foreign policy views with regard to Russia.
Clinton campaign chairman John Podesta suggested there was ‘‘a kind of bromance going on’’ between Trump and President Vladimir Putin of Russia. Or ‘‘maybe it’s simply just a mutual admiration society,’’ he told MSNBC.
The Clinton campaign says Russia favors Trump’s views, especially on NATO. Trump himself has spoken favorably about Putin as someone he could negotiate with.
Trump supporters did succeed in preventing a reference to arming Ukraine from getting into this year’s platform, but the document is far from pro-Russia. It accuses the Kremlin of eroding the ‘‘personal liberty and fundamental rights’’ of the Russian people.
There are extensive financial ties between Trump and Russia, and between Trump allies and Putin allies.
‘‘Russians make up a pretty disproportionate cross-section of a lot of our assets,’’ Donald Trump Jr. said in a 2008 interview. ‘‘We see a lot of money pouring in from Russia.’’
Russia’s ability to disrupt online communications has been the subject of several investigations.
It reportedly has a vast operation of people who are used to cause havoc online. Last year, the New York Times’s Adrian Chen explored the workings of ‘‘The Internet Research Agency,’’ as it is known. Hundreds of employees are paid to mix falsehoods with truth on social media in order to mislead and misinform.
‘‘Russia’s information war might be thought of as the biggest trolling operation in history,’’ Chen wrote, ‘‘and its target is nothing less than the utility of the Internet as a democratic space.’’
The timing of the Wikileaks release, coming immediately before the convention, is one reason that analysts suspect political disruption.
Clinton loyalists were eager to put a period on the latest e-mail episode. Governor Terry McAuliffe of Virginia, a former chairman of the Democratic Party, said Monday ‘‘we’re done’’ with the controversy. But Sanders’ delegates didn’t seem ready to move on.
And there may be more shoes to drop: James Clapper, director of national intelligence, has said US officials expect more cyber threats against the campaigns.
The latest controversy also serves as an unwelcome reminder of Clinton’s earlier problems with her handling of classified e-mail as secretary of state. In case anyone failed to make the connection, Trump was happy to tweet a reminder: ‘‘Here we go again with another Clinton scandal, and e-mails yet (can you believe).’’