I like Lyin' Ryan. I think I will use that unless something better comes along.
A nickname needs to at least have some connection to the person in order for it to work. That one has a nice ring to it, but if Ryan is not a bigger liar than your average Congressman (does not have to be in the same category as Obama, that is a high bar for anyone to reach), it is missing the needed connection and fails.
It would be like saying "Queen Obama", the implication of which is that he is a transvestite". It is missing the connection to Obama and fails (also fails because it sucks).
You can use it, of course, but it would be as stupid as someone calling Obama a Muslim.