A320 Captain reports that the nosewheel steering disconnect was not accomplished on the before start checklist; and was forgotten prior to pushback. Maintenance was called but no damage detected.

Narrative

About 15 minutes prior to departure; we ran the before start checklist. The last step; 'Nosewheel Steering Disconnect - Displayed' couldn't be completed because the ground crew had yet to install the pin. The First Officer and I discussed this; and I planned to talk to the push crew as soon as they hooked up on the headset. The First Officer failed to follow his normal technique of placing the checklist in the middle of the throttle quadrant when a checklist has been run; but is not complete. I failed to do my normal technique of placing a piece of paper hanging on the dash in front of me. We ran the before pushback checklist at departure time and we pushed with the pin not installed. I asked the push crew as we neared the end of the push if the pin was in. They said it wasn't. We wrote it up; had a mechanic come out and inspect the nose gear. All was well and we departed. We completely forgot about the pin after running the initial checklist until we were already into the pushback. Both of us have techniques to address this; but we both failed to do them. There was a lot going on at the time of push; the jetway was having a problem with the power cord; we were getting close to push time and we had the normal time crunch as the push approached. This isn't an excuse; but these 'normal' distractions certainly didn't help us. I'm sure both the First Officer and I will do better next time.