(CNN) - A request by the Senate Intelligence Committee for Florida's US senators to send a letter on Russian hacking threats to state election officials was made only to Florida and not the senators of any other state, the committee's top Democrat told CNN on Wednesday.
Virginia's Sen. Mark Warner said he and Senate Intelligence Chairman Richard Burr asked Florida's Sens. Bill Nelson and Marco Rubio to send their July 2 letter to the Florida secretary of state warning about the threat of Russian election hacking and encouraging the state to work with the Department of Homeland Security, a request they haven't made to other senators.
"In an abundance of caution we asked, and DHS has acknowledged they thought that letter was very helpful," Warner said. "That's the only request we've made."
Warner declined to explain why he and Burr, a North Carolina Republican, had requested the letter from Nelson and Rubio. Warner and Burr have declined to confirm or deny Nelson's controversial and unproven claim earlier this month that Russian hackers have "already penetrated" state voting systems.
The claim has become an issue in Nelson's Senate race against Florida Republican Gov. Rick Scott, but the Florida Democrat hasn't backed down from it, and he has pointed to his July letter sent with Rubio. The letter said the Senate intelligence panel had found it was "possible that additional activity occurred and has not yet been uncovered," though it did not describe any kind of hacking attempt against the state like Nelson described.
Nelson has said he was referencing information that was classified, and he has not provided more details. But the Florida secretary of state's office, which has criticized Nelson's public comments, said in a letter last week that some state election officials have a clearance to receive such information, and none has been provided.
DHS sent Florida's secretary of state a letter Tuesday that stated: "We have not seen any new or ongoing compromises of ... election infrastructure in Florida."
Responding to questions sparked by Nelson's comments, Burr earlier this month sent a letter to the Florida secretary of state that didn't confirm or dispute Nelson's claim, instead asking local officials to consult with the FBI and DHS.
Rubio, a Republican who is on the Senate Intelligence Committee, has taken a line on the controversy similar to Burr and Warner's. Asked Wednesday whether Nelson had made a mistake, Rubio said, "Well, he's engaged in a campaign so these things come up in campaigns."
"I really don't want to politicize this issue. I don't want to create the impression that there's no problem, because that's not accurate," Rubio added. "There is always an ongoing threat, not just for Florida, but for every state in this country."
Warner declined to discuss this week's letter from DHS or the specifics of Nelson's statement. But he said the federal government still faces a challenge in gaining the cooperation of state and local election officials.
"We still have a challenge. One of the challenges -- and it's not a critique of DHS or FBI, since this is a whole voluntary system -- how do we make sure even when a district is notified that they do full mitigation?" Warner said.
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