We spoke with Nathan Hochman, a former Assistant U.S. Attorney General who is running to replace Gascón as L.A. County's D.A., on "TMZ Live" Friday ... and, he tells us he finds the timing of GG's announcement "incredibly suspicious."

Hochman points out the habeas writ was filed last year in May, and the motion for resentencing was filed in February ... so, if D.A. Gascón really thought Erik and Lyle deserved to get out of jail, Hochman asks, why did he wait to advocate for it?

NH says a rash of poor headlines -- including the story of a double murderer who was recently released after less than four years in prison -- forced Gascón to pull a desperate maneuver and let the Menendez brothers out.

Hochman says Gascón is gaslighting the public by claiming he took a second look at the case because public interest spiked in light of a new Netflix documentary ... saying he's been aware of this new evidence for more than a year.

As you know, Gascón held a press conference Thursday saying he'd ask a judge to resentence Erik and Lyle from life without the possibility of parole to life with the possibility of parole. With time served, the brothers will be eligible for parole so long as the judge assigned to their case -- William C. Ryan -- signs off.

FWIW, Gascón said during the press conference that the election has no bearing on his decision to push for their release.

The two may still have to go through the parole board ... though defense attorney Mike Cavalluzzi says the judge could use his own discretion to change the sentence.

As of earlier this month, Hochman had a 30-point lead over Gascón, according to the L.A. Times -- so, George does have quite a bit of ground to make up.