It is irrelevant, his money he can waste it if he wants, but they will never have enough votes to repeal the second.
Bill Gates isn't trying to repeal the second amendment.
What he's try to do is help get reasonable gun safety laws passed.
No one will lose their guns. The only thing that initiative will do is require background checks to prevent criminals etc from illegally purchasing a gun or even have a gun.
If you're not a felon or have mental issues or a history of domestic violence etc this law will never effect you beyond having to fill out a form.
I can't believe that people would want a criminal to be able to just walk into a store and pick out the gun they want to use in their next crime.
Oh and he's not wasting his money, that ballot initiative will pass. If you know anything about Washington state you would know that the majority of the population is in the Seattle/Tacoma/Everett area and it's nothing but liberals. Liberals out number the conservatives in Washington so on a state wide vote, conservatives usually lose.