For an elected official to serve as a "delegate" means that the voters of that state or district want the person they elect to represent their interests. They're not saying, "We voted for you because we trust you to do what's best for us." They're saying, "We've indicated to you what we want and need for this state or district, so we want you to go to Congress and work for those things on our behalf."
When voters feel this way, elected officials will feel they must carry out the will of the voters in their state or district or risk being removed from office when the next election occurs. Since representatives to the House serve only two year terms, while members of the Senate serve six year terms, you can expect the delegate theory will affect the US House representatives more immediately and prominently. Their actions in office will still be fresh in memory when the next election cycle occurs. Senators have a longer time to establish a track record that will earn the trust of their constituents.
