There is no doubt that this issue has been raised at this time, and jumped on by the Tory supporting newspapers, because of the proximity of the local elections and their fear that the results will be affected by Partygate and the Johnson lies.
But does anyone seriously not think that if the situations were reversed the Labour Party and the left leaning newspapers wouldn't be doing exactly the same thing?
There may or may not be anything in these allegations but this is all part of the dirty world of party politics, and if there is any chance at all of the mud that is being slung around sticking it is a legitimate, if unpleasant, tactic.
FWIW I have no more reason to believe that Starmer is completely innocent in this than I believed the serial liar Johnson over the Partygate lies, and cynically believe that it is possible that the Durham police have not investigated it to the same level as the Met did with Partygate.
There will continue to be a fuss until Durham police make a statement to say that they have looked into this and are satisfied that no rules were broken, otherwise Starmer just has to ride it out the best he can.