Former Democratic House candidate Hans Keirstead was the target of a successful cyberattack during his campaign in California’s 48th District against pro-Russia GOP Rep. Dana Rohrabacher. 

Rolling Stone reported that in August 2017, Keirstead fell for a phishing email that asked him to enter his password for his work email address, which he also used for his campaign. The campaign also reported efforts in December to hack into the campaign’s website and “hosting service,” and an effort in January to hack into the campaign’s Twitter account. Only the phishing attack in August was successful.

It is not immediately clear who was behind the cyberattack, but national security officials have been warning of Russian attempts to penetrate election systems and campaigns themselves. Congressional campaigns are not always well-equipped to combat those attacks, but some party organizations and outside groups are taking steps to educate campaigns about how to secure themselves.

Keirstead, a stem cell researcher, came in third in the June top-two primary, missing a spot on the November ballot by 125 votes. The second-place finisher, fellow Democrat Harley Rouda, a businessman, will face Rohrabacher in the fall. Keirstead’s campaign manager told Rolling Stone that he did not believe the cyberattack affected the outcome of the primary. 

Rouda’s campaign did not immediately respond to a request for comment on the cyberattack against Keirstead. 

The 48th District is a top target for Democrats looking to take back the House, since it is one of seven GOP-held seats in California that Hillary Clinton carried in 2016. Inside Elections with Nathan L. Gonzales rates the race Tilts Republican.