This is my favorite (today) from Black Sheep
Less about the election than the larger crisis is Mary J. Blige and Big Boi's "Sumthin' Gotta Give":
He recently released an English-language version, but the Spanish original of Andres Useche's "Si Se Puede Cambiar" is (IMHO) much better both politically and lyrically.
Jose Conde's "Respondele a Obama":
Dirk Powell's Zydeco "Oui on peut"
Of course we can't forget Will.I.Am: