I'm on a Continental ticket going DCA->MIA->DCA to catch a cruise in May. The thing is on the way down, I'm on a NW codeshare with a bad connection (3 hour connection at DTW). Checking the schedules I noticed CO has a connecting flight through EWR which would get me an 1.5 hours earlier.

What are my chances of showing up at the CO ticket counter and asking to standby on the more direct routing?