There are at least three ways which lead a representative or a senator to vote for or against a bill or amendment: representational, organizational and attitudinal. Representational is based on the assumption that members want to get re-elected and therefore vote to please their constituents. Organizational is based on the assumption that since most constituents don’t know how their senator voted, it is not essential to please them. But it is important to please fellow members of Congress. The attitudinal is based on the assumption that there are so many conflicting pressures on members of Congress that they cancel one another out, leaving them virtually free to vote on the basis of their own beliefs.
The representational view has merit under special circumstances, like when the constituents have a clear view on some issue and a legislator’s vote on that issue will draw much attention. For instance, a legislator from a highly black district won’t vote against a civil rights bill for minorities, while representatives with mostly non-minority (white) voters in their district can vote whichever way they please on the issue. Foreign policy is generally remote from the daily interest of most Americans and the public changes opinions on it rather rapidly.
The constituents and the legislator vote differently for the most part on foreign policy. When an issue arouses deep passion among voters, it is necessary for the legislator to go in accordance with the majority constituents, despite his or her personal convictions if he or she wants to be re-elected. The general problem with representational explanation is that public opinion is not strong and clear on most measures on which the Congress votes. Many representatives and senators face constituencies that are divided on key issues.
The organizational view deals more with legislators voting in accordance to cues provided by other legislators. Party plays a principle role in cues, most legislators will vote according to their party’s will. But party and other organizations do not have clear positions on all matters. For most, a legislator is likely to be influenced by members of his or her party on the sponsoring committee. If there is no obvious liberal or conservative position on the matter the legislator takes a cue from the committee reviewing the bill. If they vote for it, so does the legislator, against it, so is the legislator. If the vote is split, the legislator will vote the same manner as another legislator with similar beliefs (maybe he knows more about the bill than you do, you were sleeping through the last hearing).
The attitudinal view is based on the individual legislator’s personal ideology. Where party splits, it is up the legislator to make the decision. Often times, senators from the same state may have widely differing opinions on certain issues based upon his or her ideology. A legislator who is a liberal Republican may vote democratic on some issues, and a conservative Democrat may vote republican on other issues.