Wallace,
Since the internal resistance of the windings in the solenoid is constant, it follows therefore (according to Ohm's law) that current and voltage would play a part in the function of the solenoid. Meaning that a lower voltage would result in a lower current flow through the windings (current = voltage/resistance).
Without going into too much technical detail, the strength of the magnetic field produced by the windings is in turn related to the amount current flowing through the windings.
That is why the solenoid is a little sluggish when the ignition is on, fuel pump running and engine off (the overall voltage in the system is lower).
With the engine running, the voltage increases and so does the available current and hence the solenoid perks up.
So, the short answer to your question is: yes.
I would suggest that you try to readjust the switch after cleaning it and see if fouling of the contact points happen again.
If it does, then we can look further.