"In this highly politicized environment, it may be tempting to make such accusations rather than examine the forces creating an unsustainable public exchange marketplace, but they do not move us toward fixing the problem," he writes.

Aetna's argument appears to have convinced at least one Democrat in its home state of Connecticut. Sen. Chris Murphy told the Hartford Courant that there was "simply no basis" to believe Aetna's business decision was political. Murphy might be giving cover to the insurer in the hopes that it will keep its headquarters in Hartford, an otherwise economically challenged city that some have suggested it might abandon if it goes through with its merger.

Aetna is certainly not alone in expressing concerns about the financial viability of the ACA exchanges. UnitedHealth, the nation's largest insurer, announced earlier this year that it would abandon most of its exchange business, citing an inability to make a profit.

But what struck observers as fishy about similar announcements from Aetna and Humana in August was that they came right after the U.S. Department of Justice announced that it would challenge their proposed merger in court. In addition, both companies had expressed optimism about their exchange business only months earlier, even indicating that they would expand in the coming year.