Officially, no. Neither Same-day change nor standby allow for change of airport (with "Multi-airport cities" like JFK/LGA being a possible corner case, but not EWR).

Once you're at the airport, or if there's any type of IRROPS, then anything is possible and it doesn't hurt to ask - but the odds of you succeeding are at best very low.

As an example, a few days ago I changed from PHL-IAH-SJC to PHL-SFO over the phone a few hours before flight. Technically that's not allowed, but my PHL-IAH was delayed and my connection was looking unlikely so they were happy to make the change.