Roughly 2.6 million people die each year in the US. A story making the conservative rounds has a former Justice Department official noting that four million dead folks are on the rolls. That might well be plausible, as it would have officials having a year and a half of dead folks on the rolls.
Officials want to keep things accurate, but also want to err on the side of not pulling actual live voters off the rolls. This The Hill piece noted Ohio fending off a lawsuit when they wanted to prune folks who hadn't voted in three straight federal elections off the rolls. This passage gives credence to the four-million assertion-
To remedy that problem, [Ohio Secretary of State] Husted said the state worked to bring its rolls into full compliance with federal and state laws, removing nearly 340,000 deceased voters and 1.3 million duplicate registrations.
If Ohio pruned off 340K, four million nationwide isn't too much of a stretch.
However, that's not news. It's only news if you leap to the assumption that those four million are going to be voting Democratic a la the old saws of Daley-machine pols getting the Chicago graveyard vote counted to pad statewide totals.
I'm reminded of the Hugh Hewitt aphorism; "If it isn't close, they can't cheat." That's better read as "If it isn't close, cheating won't make a difference." It wouldn't be that hard to forge a dead person's signature to a absentee ballot application and cast the dearly departed vote (or one of those living non-voters Ohio wanted to purge) to pad your guy's vote total. It would be hard to forge 5,000 of those in a single state without someone double-checking.
Can folks take advantage of lax ID laws to vote in multiple places, or impersonate someone? Yes.
Can folks get out the graveyard vote? Yes.
Could someone hack the computer software in election systems? Yes
Can they do so comprehensively enough to swing an election without getting noticed? Good question.
A systematic effort to run up the graveyard vote should be noticeable. Likewise, a large-scale effort to double-vote or impersonate voters will likely lead to someone talking or a tell-tale e-mail (something our friendly Russian hackers would be happy to scrounge up if they existed) wouldn't stay secret for long. It might well be underplayed by "Democratic operatives with bylines" but there's enough non-MSM outlets for the truth to win out, as well as some honest left-leaning reporters who aren't going to drink that much Kool-Aid.
We're also assuming that it will be the Democrats that are the ones that are doing these shenanigans; a fairly safe, but not iron-clad assumption, for Democrats don't have a corner on political corruption.
Thus, the rigged-election meme that Trump has been playing with, including last night's debate, is somewhat overblown. We'd need something of a perfect storm for it to come to fruition.
(1) We'd need the presidential race to be close
(2) We'd need Trump to win the honest vote in a state by a squeaker
(3) We'd need Democratic operatives to be running enough electoral black-ops to swing things over to the Democrats.
(4) Said operatives have to run with enough cunning and secrecy to evade notice.
(5) State officials have to either not notice the black ops or be in on the game.
Item 5 would require a Democratic state government to be truly effective, since significantly abnormal returns in Democratic areas would be triggers for double-checking. Item 3 assumes a KGB/CIA level of competent spycraft, and the former would seem to prefer Trump.
Lastly, item 1 has to come into play; if the current numbers hold up, suppressing the graveyard vote won't be enough to get Trump over the finish line.
Could that scenario happen? Yes. It isn't likely and would require a Tom Clancy-thriller level of coordination. They'd have to be both very nasty and very competent to pull that off, and the latter seems unlikely.