Moshiach will possess all the possible positive qualities. These qualities are a reflection of G-d's, expressed through Moshiach due to his complete unity with Him. These qualities will have the power to affect even the lowest parts of the world, revealing the oneness of the world with Hashem. 

So, will Moshiach be a Democrat or Republican? The answer is that Moshiach will possess the good qualities of any party of philosophy.