It depends on whether you want the transaction to be "picked up" (broadcast) again or if you want it to be dropped by the network.  If it's already marked as "local" in your Electrum wallet, I wouldd suggest simply deleting old tx and creating a new one (using the same inputs) with a higher fee.  This way, you can be sure that your transaction gets picked up by the network and processed.  The current recommended transaction fee (medium priority) is around 42 sats/vbyte.