Pros- Appeals to those who think the vote is being stolen & riles up the base
Cons - Doesn't say how to stop the steal. Middle America is not convinced there is a steal. You need to convince people there was a steal before they'll try to help you stop it...
Do you think that a bunch of Trump supporters wearing MAGA outfits chanting Stop The Steal will convince anyone that a wrong is happening. You might as well scream "Lock her up".
You need to appeal to those outside of your echo chamber.
Look at it this way. In persuasion, you need "pacing then leading".
First you need pacing (hey there, these are interesting election anomalies) then leading (STS).
#StopTheSteal alone is staring at a mirror and screaming at yourself.
Cons - Subtly hints to count only legal votes (too nuanced for many). Is very similar to #CountEveryVote, a slogan used today by the Biden camp. The word "legal" lacks reference points to those out of your bubble.
Both these slogans/hashtags are weak. Both are non-specific. One is boring. You're not going to interest or convince most people. Outsiders will see you as partisan sore losers.
Democrats are arguing at their protests that Republocans are trying to steal votes from minorities. It's evident that Republicans are trying to block mail in ballots.
Your slogan must be direct, clear and immediately decipherable to those lacking context and outside of your orbit. Your propaganda must counter that of your opponent.
Will your audience grock your message? Will it resonate with the man on the street?
Pros - The meaning is broad, clear and simple. It's also non-specific in a way that makes it relatable. Makes a binary distinction: Real vs fake. The voter reads this and thinks, "I made effort to cast my vote. Make damn sure that only real votes are counted."
It implies that the lefts #CountEveryVote is a demand to count fake votes.