There’s suddenly a great deal of discussion about the possible rigging of the forthcoming presidential election. Donald Trump has argued that it can be rigged – perhaps that it is being rigged – although he seems short on specifics or evidence.

In response, many – including some in the media as part of their “fact checking” role – are trying to assure the public that the election cannot possibly be rigged; that any claims that such a thing might even be possible are “false” or “not true.”

Quite apart from the fact that it is usually impossible to prove a negative, these reassurances seem to be false. Election computers have already been hacked, other hacking has resulted in the release of documents quite capable of affecting the election, both federal and state officials are taking steps aimed a preventing such interference, and a few professors and others have shown how easily such an event could occur.

Although I was hacking as far back as the 1950s, and created a computer technique for determining the chance that any small group of voters could change the outcome of a presidential election – now called “The Banzhaf Index” – which has been widely adopted and utilized, I certainly don’t ask you to take my word for it. On the contrary, the evidence very briefly outlined below shows that it is possible (although clearly not probable) for an election to be hacked.

Listen to Prof. Banzhaf discuss this on Breitbart News Daily on SiriusXM:

Considering the enormous consequences if it were to actually (or even apparently) occur, we must accept the fact that it is true, in the same sense that it is true (although again not probable) that our electric distribution system, airplane flight control system, banking systems, etc. could be hacked.

Moreover, while it may be difficult for hackers to actually change the outcome of the election, it is at least possible – in the same sense that many responsible people now agree that computer experts might be able to hack into the nation’s banking system, electricity distribution control system, air transit systems, etc.; as they have with so many major governmental organizations and powerful corporations.

Perhaps more importantly, a hack could easily cast significant doubt on the validity of the election even if the election result wasn’t in fact changed, especially if the losing nominee and/or his supporters voice suspicion concerning the outcome, and thus help to undermine the faith of many citizens in the entire election process. Indeed, some 40% of the public, according to a recent survey, are deeply skeptical about the integrity of the nation’s election apparatus.

Note that if some election results appears suspicious, or only a few voting machines display clearly exaggerated results, or if the word “hacked” or a picture of Guy Fawkes appears on the screens of a few computers used to compile votes, disappointed voters could become very upset.

Here’s just some of the evidence that rigging/hacking the forthcoming election is possible.

* According to NBC news and other media sources, the CIA is currently preparing to launch an unprecedented cyber war against Russia as retaliation for what has now been clearly identified as attempted Russian interference in the forthcoming U.S. presidential election. This definitely includes the recent hacking of the election systems in Arizona and Illinois, and probably the release of emails damaging to Democrats for which Russia is also believed to be responsible.

* Also, Homeland Security Secretary Jeb Johnson is considering designating election systems around the country as a “critical infrastructure” in need of federal assistance and protection, and has already established an Election Infrastructure Cybersecurity Working Group, as well as launching a Voting Infrastructure Cybersecurity Action Campaign.

* Meanwhile, an anonymous Homeland Security Department official reportedly said that the voter systems of more than 20 states – including the key state of Florida – have been targeted by hackers just in recent months.

* The FBI’s reported that the data bases of election boards in at least two states were successfully hacked, apparently by foreign governments, and in at least one case the hackers were able to insert malicious software into the system. Moreover, their report showed that both infiltrations were done using common off-the-shelf software programs readily available to anyone who wants them from the Internet. In other words, hacking election machines can be done not only by hostile governments and master computer experts, but also by common garden-variety hackers.

* Just weeks after the release of a report showing how easy it would be for Russians or even high school nerds to hack a presidential election, two other professors have just proven it. University of Michigan Professor Alex Halderman was able to infiltrate a voting system from 500 miles away, and, in another demonstration, manipulate voting results with only a screwdriver and some memory chips. Princeton professor Andrew Appel was able to hack an election machine in only 7 minutes.

* According to an official from the Department of Homeland Security, 25 states have reached out for federal aid related to election security, and DHS Secretary Jeh Johnson said he hopes more will seek assistance.

* CNN reluctantly reports that “we’ve officially entered the era of the hackable [presidential] election.”

* Mother Jones reports that “the concern that somebody might try to hack voting machines no longer seems outlandish.”

* Politico says a computer expert remarked that if some of the more susceptible voting machines hadn’t yet been hacked, “it was only because no one tried.”

* Money magazine says we’ve officially entered the era of the hackable election.

* Wired claims that the move toward electric voting machines turned out to be a “technological train wreck.”

*ABC News featured a piece entitled “Yes, It’s Possible to Hack the Election.”

* Tarrant County, Texas, is now investigating voter fraud through the use of mail-in ballots.

Despite the lack of real support or substantiation for the claims Trump is making about a rigged election, all of the above is more than ample reason to believe that many recent developments now make elections subject to being hacked, if not rigged.

These include the increased use of electronic voting machines (especially where they leave no paper trail), that more and more computers and data processing devices used in the election process are connected to the Internet, and that some states permit residents to cast their votes over the Internet.

Also, under our Electoral College system, any rigging or hacking which resulted in a change in even a very small number of votes, and perhaps even only a small number of votes in one individual state, could change the outcome of the presidential election, something very unlikely to occur were there to be a direct nationwide presidential election.

In this regard remember how the 2000 presidential election was decided by fewer than 1000 votes out of almost 6 million cast in Florida; so a hack of as little as 550 votes could have resulted in a different president.

In short, even a very small probability that an election could be hacked, just like the small possibility that hackers could disable our power supply, airline system, etc. must be taken seriously and reported to the public, considering the gravity of the harm which would be caused.

Indeed, the risk of a hacked or rigged election might be even greater. Power and airline systems which have been hacked should be able to be fixed and back to normal shortly, but damage to the faith of citizen in their voting systems would have long lasting effects.

In summary, while I do not support, in the absence of any hard evidence, that the forthcoming election has already been rigged for or against any party or any candidate, or that any such rigging is likely or even probable in the near future, we should be wary of even the very small probability of an election hack.

To paraphrase a well-known James Bond movie: “Never Say Never.”

John F. Banzhaf III is a nationally-known expert and professor of Public Interest Law at George Washington University Law School. He is a FAMRI Dr. William Cahan Distinguished Professor, a Fellow of the World Technology Network, and the Founder of Action on Smoking and Health (ASH). Follow him on Twitter at @profbanzhaf.