Politician lives by taking credit on good things happening to the constituents. Whether he really made it happen or not is another matter. The important thing is getting credit because it will boost his social and political capital to get elected.
This obsession means that they wouldn't do the right thing if they feel they can't get any credit for it. Don't even think of doing something unpopular but essential as it will erode their standing.
Heck, they'll even block a good thing just because they don't want other politicians to get the credit.