The FBI reportedly investigated a series of cyberattacks against a Democratic candidate seeking to challenge incumbent Rep. Dana Rohrabacher Dana Tyrone RohrabacherDemocrat Harley Rouda advances in California House primary Lawyers to seek asylum for Assange in France: report Rohrabacher tells Yahoo he discussed pardon with Assange for proof Russia didn't hack DNC email MORE (R-Calif.) earlier this year.

Rolling Stone reported Wednesday, citing documents and interviews with campaign officials, that Democrat Hans Keirstead was targeted by hackers during his congressional bid starting with a phishing attempt in August 2017.

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Keirstead fell 125 votes short in the June 5 nonpartisan "top two" primary for the seat in California’s 48th Congressional District. He has endorsed fellow Democrat Harley Rouda, who is challenging Rohrabacher in November's general election.

Rohrabacher is considered one of the most pro-Russia members of Congress and is a vocal supporter of President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE.

Rolling Stone noted that the source of the cyberattacks targeting Keirstead, who is a stem cell scientist, is unclear.

The agency did not comment for Rolling Stone's report, and Rohrabacher's campaign didn't respond to requests to comment for the story.

The FBI declined The Hill's request for comment.

"It is clear from speaking with campaign professionals around the country that the sustained attacks the Keirstead for Congress campaign faced were not unique but have become the new normal for political campaigns in 2018,” Keirstead's former campaign manager, Kyle Quinn-Quesada, told Rolling Stone.

Quinn-Quesada added that the campaign did not believe that the cyberattacks had an impact on the primary election results.

The magazine reported that Keirstead was first targeted in August 2017, when he received the phishing email to his work account and entered his password, before realizing it was a fake message. He then ordered his office to strengthen its email security efforts.

Rolling Stone reported that hackers or bots aggressively tried to access the campaign's website and tried to gain administrator access to its server through the cloud-server company hosting the website, but were unsuccessful.

Unknown individuals also unsuccessfully attempted to access the campaign's Twitter account in January, according to the magazine, and Keirstead's biomedical research company was also briefly hacked during the same month.

Quinn-Quesada told Rolling Stone that he informed the Democratic Congressional Campaign Committee (DCCC) and the FBI about the attempted cyberattacks, including the successful phishing attempt on the candidate's work email account.

Emails obtained by the magazine show that the DCCC’s top IT executive and the group's chief of staff were both told of the attempted attacks and that the organization shared the information with the FBI.

The DCCC did not immediately return The Hill's request for comment.

The targeting of Keirstead's campaign is the latest report of attempted hacks in the 2018 midterm elections. The Daily Beast first reported last month that staffers for Sen. Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (D-Mo.) were targeted by Russian hackers. McCaskill is one of three targeted candidates first referenced by a Microsoft executive last month.

A Microsoft spokesperson declined to tell Rolling Stone if Keirstead was one of the three candidates, citing customer privacy.

Special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE last month indicted 12 Russian military officers in the 2016 hack of the Democratic National Committee.

Updated at 4:57 p.m.