The U.S. government on September 22 notified 21 states that their voting systems were targeted by hackers in last year's presidential election, and several of the most closely contested states said the hackers were linked to the Russian government.
The so-called battleground states of Wisconsin, Ohio, Colorado, and Minnesota, where Democratic candidate Hillary Clinton lost in some cases by only a few thousand votes to then-Republican candidate Donald Trump, were among those that blamed Russian hackers.
AP reported that the battleground states of Florida, Pennsylvania, and Virginia also were targeted by hackers.
Alabama and Washington state, which were among the majority of the 21 hacked states which were not closely contested in the election, also said they were targeted by Russians.
According to the states and the U.S. government, none of the hacking attempts succeeded at penetrating the states' voting systems or obtaining sensitive information about voters -- meaning the hacking efforts never got to a point where they could affect the outcome of the election.
"There remains no evidence that the Russians altered one vote or changed one registration," said Judd Choate, president of the U.S. National Association of State Election Directors.
Russia has denied any attempt at interfering in the election, with Russian Foreign Minister Sergei Lavrov on September 22 saying "nobody has ever presented a single fact anywhere" that supports the allegation.
The U.S. Department of Homeland Security did not publicly say who the hackers were. But Wisconsin Elections Commission Administrator Michael Haas said the department told the states privately that "Russian government cyberactors" targeted their voter registration systems.
Haas said he was told the Russian government tested election systems for vulnerabilities in hopes of accessing voter registration databases, but was unsuccessful.
Wisconsin was one of a handful of battleground states in the Midwest that helped Trump win the presidency. Trump carried the state by 22,748 votes, or about 0.8 percentage points.
In most of the 21 states notified about hacking attempts, the department said it observed only "preliminary activity" by the hackers. It said only a small number of networks were "compromised."
Only Illinois has reported that hackers successfully breached its voter systems.
A spokesman for Connecticut's secretary of state said Russian intruders were detected and blocked.
Colorado Secretary of State Wayne Williams said the department told his state that its systems were scanned in the weeks before the 2016 election.
"A scan is similar to burglars jiggling the doors of a house and moving on when they realize the doors are locked," he said.
Minnesota Secretary of State Steve Simon said entities at the Russian government's behest scanned the state's system for vulnerabilities, but did not breach the system.
Washington's top election official, Kim Wyman, said the state learned of attempted intrusions from Russian internet addresses last year, and immediately alerted the FBI.
Arizona and Illinois also said last year that hackers had targeted their voter registration systems.
California Secretary of State Alex Padilla said he was unhappy that it took the department so long to notify states that their voting systems were vulnerable to cyberattacks.
"It is completely unacceptable that it has taken DHS over a year to inform our office of Russian scanning of our systems, despite our repeated requests for information," he said, calling it "a detriment to the security of our elections and our democracy."
A U.S. special counsel and several U.S. congressional committees are investigating whether Russia attempted to interfere in the election or collude with the Trump campaign.
While documents leaked to the media have revealed a handful of interactions between the Trump campaign and Russians, Lavrov said at a news conference in New York on September 22 that no hard facts have turned up that prove collusion or meddling in the election.
"In about a year of this chaos...we never heard not a single fact," he said.
Lavrov said that U.S. Secretary of State Rex Tillerson told him privately that he had seen evidence of Russian meddling. But Lavrov said when he demanded to see the proof, Tillerson told him it was "confidential" and could not be shared.
Lavrov accused former President Barack Obama of inventing the alleged Russian election-meddling plot in a "small-hearted" and "revengeful" effort to "put this time bomb into U.S.-Russian relations" and make it difficult for the Trump administration to work closely with Moscow.
"And now the immense potential of our bilateral relationship stands there in vain, and our relations are contracting due to Russophobic hysteria," Lavrov said.
With reporting by AP, AFP, and Reuters