You have the option of selecting viewing Hot or New. Hot is by popularity - a combination of upvotes, views, comment activity. Downvotes also affect memes, sending them back down the line.
The same crew that attacks every meme not in favor Trump as soon as it comes out the chute are also downvoting them, which is why nobody else gets to see them unless they go directly to the source's account.
It used to be worse - if you got enough downvotes, a meme could get unfeatured, so it wouldn't appear in your profile at all.
That's on the main Politics stream. In politics3, they don't congregate there, so when you look at my profile, you might see them topping my page sometimes.