During the primary election process, states' interests are largely ignored. Voters can choose people in the primaries that align with their interests, but the politicians are looking to cater to as many people as possible. Therefore, they'll make general promises without actually helping a given state in any noticeable way should they become president.
Primary elections are mostly to consolidate party power. In some instances they can benefit states - bringing extra revenue from conventions, and publicity for states, but for the most part they aren't intended to help the states. If a party in power has a states' rights candidate, and his or her party is the prevailing one, that can indirectly benefit states, but not all states.