What is balanced party line?

It should also be noted that while the overwhelming majority of elected officials do identify with a political party, the political parties of the United States are much more individualistic than in other political systems (i.e. in a parliamentary system). More often than not, party members will "toe the line" and support their party's policies, but it is important to note that they are free to vote against their own party and vote with the opposition ("cross the aisle") if a particular policy is counter to the priorities and interests of their constituents. Recent examples of this can be seen in such highly controversial matters as Social Security reform, the federal budget, and some environmental policies.