The 23-year-old central midfielder has one year left to run on his current contract with the Dons and there is no sign of an extension on the horizon.
Portsmouth boss Danny Cowley is also keen on Charlton Athletic midfielder Alex Gilbey, who has also entered the final year of his current contract with the Addicks.
McCormick was unable to prevent Wimbledon’s relegation to League Two in the 2021/22 season but could be offered a way back to League One with Portsmouth making a late push to sign the midfielder.
The central midfielder is also a target for Joey Barton’s side, who have made their sole midfield signing so far this summer in defensive midfielder Jordan Rossiter from Fleetwood Town.
McCormick made 47 appearances in all competitions for the Dons last season, scoring eight goals and laying on nine goals.
The Gas are set to lose Zain Westbrooke and Alex Rodman, who no longer feature in Barton’s plans, leaving them spots to fill in the heart of their midfield and on the wing, respectively.
Bristol Rovers began their campaign with a loss at home to Forest Green Rovers, followed by successive wins over Burton Albion and Oxford United.
Portsmouth began their League One campaign with successive draws against Sheffield Wednesday and Lincoln City followed by a win over Cheltenham Town.
The Gas will next travel to Barnsley on Tuesday and Pompey will play host to Cambridge United on the same day.
