It is possible to pick a side and stick to it, though there will be trade-offs for doing so. I have not played through the single player campaign, but I would assume that it would be balanced so you have the entire range from trying to keep everyone moderately happy to blatant pandering to a specific race being viable options (the former probably being easier). I think for my first game I'll go on an issue by issue bases, without considering the consequences to race reactions.
