This is a case where no waivers/no favors might actually hurt the airline. But only if certain conditions are met.

To answer your question the rule states SAME DAY. I would hope though that there was still some discretion with the supervisors.

I could see two scenarios where the airlines win and you win by them making an exception. The first would be if the flight you bought appears to be seriously oversold, the second would be if there is a weather situation approaching one of your airports and NWA puts a "weather waiver" into effect.

If your flight is oversold and you are willing to go a day earlier than the airline benefits by not having to deny boarding to someone, as long as the flight you are looking at has good availability.

If there is weather approaching they generally give a variance of a few days to a week and are very willing to accomodate requests.

If neither of these scenarios are in place, begging is the only thing. Of course with the new security thing, I am not sure standby on another day is an option since you need a boarding pass to get to the gate to see if you can standby. If either of the two scenarios I stated above were in place they would actually confirm you on an earlier flight and you would get a BP.

Of course with on-line check in you could actually check in for your flight and then go to the airport and hope security does not "catch" that the date is wrong. I don't know what there window is for letting someone on the concourse, I always thought the BP had to be for the date you were accessing. I really don't know.