Well-regarded political scientist Larry Sabato is delivering the latest and perhaps most damaging critique to Fox News and CNN over their methodologies in selecting which Republican presidential candidates will make it onto the stage for their respective primary debates.

In an op-ed for Politico, Sabato says the selection process based on candidates' standing in national polls is "statistically unsound," and that the Republican National Committee could have picked a better way.

"With a record 17 prominent candidates vying for the Republican nomination (so far), no system for determining admission to the debate stage will please everyone," Sabato wrote. "But the GOP can certainly do better than the statistically unsound procedures announced by Fox News and CNN. These rules will senselessly reward gimmicky candidates like reality-TV star Donald Trump and punish serious, viable ones like Ohio Gov. John Kasich."

As of now, both CNN and Fox have said they will each host one primetime debate with the 10 candidates who poll highest in an average of recent surveys.

As a consolation prize for the other seven-plus candidates who don't make the cut, Fox News is offering a daytime (likely with far less viewership) forum for them to participate. CNN has said it will offer a second "debate" to take place after the first.

Another point Sabato raised in his piece is that the candidates who are polling near the bottom of even the top 10 are statistically tied, once the margin of error is taken into consideration. (CNN has said for those candidates, it will then factor in polls just in early primary states, like New Hampshire and Iowa).

But the impact of not making it onto the main debate stage early in the primary process can be devastating to a campaign, especially of candidates who lack name recognition, such as former Hewlett-Packard CEO Carly Fiorina.

"The stakes are simply too high: If a candidate can't even make it to the debate stage, why would rational donors and volunteers continue giving money and time to what is apparently a lost cause?" Sabato wrote. "It's hard to look presidential languishing at home while your opponents are discussing foreign policy and social security on national television."

Sabato offered a solution similar to one offered by some conservative activists: Invite all current or former elected officials to participate in the primetime debates, but split them randomly between two stages, which will also include the other candidates who have not served in public office. (This, however, would not solve the problem of a likely viewer drop-off between the first half of the debate and the second half, which would stretch into almost midnight.)

The first debate, hosted by Fox, takes place Aug. 6.