Fresh off a new round of questions into the Russian attempt to infiltrate voting systems in Florida and 20 other states, U.S. Sen. Marco Rubio warned that the 2016 hackers were “probing” system vulnerabilities and he expects them to return this year with another attempt at putting U.S. elections “in doubt.”

“I’m not satisfied that anyone is doing enough, starting at the federal level — all the way to the state level,’’ Rubio told reporters Tuesday in Tallahassee, on the second day of a two-week swing through the state during the Senate recess. He said the threat is “not necessarily that they are going to break into ballot boxes and change the outcome of an election. The threat is much more nefarious than that.”

Rubio, a member of the Senate Intelligence Committee, which has held several hearings on Russian meddling in the 2016 elections, said that state and local officials have a dangerous level of “overconfidence” in their systems. More resources, coordination and redundancy in vote tabulation and reporting are needed soon, he said.

He suggested that Russian hackers could get into the voter registration systems in key counties in Florida and change the database — “eliminate people, change your address, whatever.” By hacking voter-registration lists, they will either delay or prevent people from voting and, he suggested, they could alter the “unofficial reporting system” on election night, creating doubt in the results.

“Everyone is on that website looking at the results, and the results show that Candidate A is winning by a healthy margin, but then the official results come out and it’s the total opposite,’’ he said. “There’s going to be mass chaos. There’s going to be anger. The losing side is going to argue it was a rigged election. ‘How could we have been winning and all of the sudden the results come out and we’re not anymore?’ ”

By throwing the election in doubt in an “already polarized country,” the seeds of unrest will be planted and Russia will have created the chaos it sought, he warned.

“If anyone tells you that Florida, or any state in the country is prepared to handle that, I don’t believe that’s true. It almost feels like what they did in 2016 is probing those things in the future because, everything I just described to you, is exactly what the Russians have done when they wanted to create havoc around the world,’’ he said.

The answer, Rubio said, is “recognizing what the threat is, building mechanisms in place to prevent the intrusion, building mechanisms to inform the public when those intrusions happen, and redundancies in the way we count votes and the way we announce results.”

Rubio and other senators on the Senate Intelligence Committee recently chided the current and former secretaries of Homeland Security for not sending stronger warning signs to the American public about past Russian intrusions in state election systems and for a lack of urgency to protect balloting this year.

Russian hackers tried to penetrate voting systems in at least five Florida counties in 2016. Voting systems were targeted in at least 21 states ahead of the 2016 general election, prompting Kirstjen Nielsen, President Donald Trump’s secretary of Homeland Security, and Jeh Johnson, secretary under former President Barack Obama, to launch efforts to protect the country’s election security.

There’s no evidence that any hack in the November 2016 election affected election results, but the attempts rattled state election officials and prompted the federal government and states to examine the way votes are counted.

The Florida Division of Elections will spend $1.9 million to work with all 67 county supervisors of elections to improve network monitoring of county voting systems, said Sarah Revell, spokeswoman for the Florida Department of State. The network monitoring system, called ALBERT, “provides automated alerts about system threats that will allow the counties to respond quickly when data may be at risk,’’ she said.

“Cyber security is an ongoing process and as we move forward, we will continue to build on our existing infrastructure to maintain the integrity and security of Florida’s elections in the future,’’ Revell said.

The governor asked legislators to fund five positions devoted to securing the state database that keeps track of 13 million Florida voters but the request was rejected.

Rubio said the Senate Intelligence Committee should have its report completed soon, but that among its proposals is an effort to expedite clearances for state and local officials who might need access to intelligence threats to their elections systems.

“Suffice it to say it’s not just about Florida,” he said. “Whether it’s pride or a sincere belief, there is a level of overconfidence about our system that we should be careful about.”