When you like something or tweet something.. you are publicly showing your support.
I have 900 facebook friends. When I like something.. all 900 see that I have thrown my support to a particular candidate and they also see his or her name.
Same with tweeting.
Just like wearing a colored ribbon to show your support for gays rights, breast cancer etal.
It therefore is exactly what I first posted, it makes you "feel warm and fuzzy" just like a good liberal would.
Like and tweet are two ways to say "attaboy" but the pol still just wants your money {or if you live in his district, your vote}.
I like you conservativeman, boy do I feel good now.