Complex sentence: She argues in "Pitfalls" that, as power has devolved to local government, local officials who at first favored reform later came to oppose further reform which might limit their discretion and so make it harder to trade power for money and money for power.
Split into simpler sentences: She argues in Pitfalls that as power has devolved to local government during reform, officials who at first favored reform. Later many local officials came to oppose further reform that would limit their discretion and so make it harder to trade power for money and money for power.