Some candidates win but disappoint their supporters and even themselves . They achieve little or nothing of what they hoped to do. Hiring staff who don't personally share their policy agendas.
Personnel is policy.
Staff who lack enthusiasm or their bosses' priorities prevent elected officials from doing what they intended to do in office. Not keeping campaign promises. These days voters have little tolerance for incumbents who break their word. Not paying attention to the interests of the coalition which elected them. Incumbents lose their allies when they don't vote right sponsor key legislation or sign allies' fundraising letters and aren't there when their friends need them.