You can’t just call someone up out of the blue and ask them for a major gift to your campaign. Period. Full stop.
This won’t work any better than building a house before you’ve found the right location, created a blueprint, laid a foundation and brought in just the right crew to build according to your specifications.
In both cases, first you must lay the groundwork. I like to think of this as making sure all the pre-conditions to a successful ask are in place before I make someone an offer I know they won’t be able to refuse. And I’ll know I’m ready to pop the question because first I’ll have answered “Yes!” to all of the ten questions that follow.