UDS, you are arguing a strawman. Nobody is discussing a position where *if *Gore had got more votes, he would have been elected. We are discussing the situation, clearly described in the OP, where Gore lost the election *because *of the electoral college system.
That’s certainly an erroneous argument. The argument is that Gore lost the election because of the electoral college, and thus a popular vote would have produced a different result. As already noted, there is no reason to believe the result *would *have been different, thus the argument is erroneous.
As far as the logical fallacy goes, it isn’t clearly any formal logical fallacy. It’s just a flawed argument.
It has elements of multiple fallacies, but it doesn’t squarely fall in any of them. In fact I imagine that different proponents are applying multiple fallacies at the same time, with different emphasis on each.
Begging the Question: Gore would have won if the system was popular vote, therefore we need a popular vote. The premise that Gore would have won is at least as spurious as the claim that a popular vote is required.
Post hoc ergo propter hoc: Gore lost following a collegiate vote, therefore Gore lost because of the collegiate vote. Just because Gore lost following a collegiate vote doesn’t indicate that the collegiate vote caused the loss. It may just indicate that the Gore campaign platform was impossible to sell over the Bush platform given the resources of each campaign. In 1991 Toyota Corollas outsold Volvos, and Toyota had a bigger advertising budget. But even with advertising I doubt Volvo could have outsold Corolla. With a popular vote maybe you still couldn’t have convinced most Americans to buy Gore over Bush. You could only do that because under a collegiate system Bush spent less effort campaigning in some populous states.
Affirming the Consequent: In the election where Gore and Bush campaigned for electoral college votes, if the outcome had been decided by popular vote then Gore would have won. Therefore if the outcome of all elections were determined by popular vote, Gore would have won. Nope. If the election had been popular vote then both Gore and Bush would have campaigned differently and the outcome is unknowable.