I don't think so, unless you straight out told them you are a registered Republican who hates Democrats or something. I'm sure they would want you to vote for Democratic party candidates regardless of what party you belong to. Probably has more to do with their signing habits than anything else.

Nah I don't mention party affiliation nor am I a staunch Republican. The two Dem ex-Presidents are just frustrating me more out of office then they ever did in office ;P

No, I don't think it matters. I doubt the person who is in charge of sorting mail has the time to look up your party affiliation. You don't deliberately mention that you are a Republican when writing to former Democratic Presidents, do you? This wouldn't be the brightest of ideas now would it? Even if you did so, I doubt it would make a difference.

Khackdrums

Just thinking outloud. I'm a registered Republican, and have gotten back an authentic from George HW Bush and an AP from George W Bush. I have gotten multiple PPs from both Jimmy Carter and Bill Clinton, cannot seem to get even APs from either of them despite multiple tries.