I really can't comment, since this is basically the scenario of my TL, Jesus Walks, and the 1980 elections are just around the corner.
It's different enough that I can say that Carter would probably fight tooth and nail to not let it turn into a war. The public would still likely view him as being completely out of his depth for allowing the attack to happen, even if it was a decisive American victory. And Reagan can still ream him on the economy.
If it fails, the Iranians might try to save face by disavowing the attackers, but there is still the issue that US Marines just massacred a crowd of students; so US-Iran relationships will deteriorate rapidly on both sides, that's if the US doesn't cut ties immediately after the attack.
I really don't see how this could lead directly to a second Carter term. Carter wouldn't want a war, and neither would America that soon after Vietnam without a damn good reason. In my TL the damn good reason is that the hostages are killed, and the Iranian Hostage Crisis becomes the Iranian Embassy Massacre. In a scenario where local rebels attacked the embassy unsuccessfully, there would be little political or popular will for a war. Carter would not likely be able to use the attack to his advantage come campaign season.
So, in conclusion, it is my opinion that the scenario you present would not make a Carter re-election any more likely than OTL (which is still more likely than most people think).