Members of Congress consider four main factors when deciding how to vote on laws: 1) whether the Constitution grants Congress the power to pass the law, 2) their personal opinions, 3) their political party's views, and 4) what their constituents/voters think. They must balance representing their own views with staying aligned with their party and the voters who elected them. The Constitution only gives Congress specific, limited powers, so they must consider whether a law falls within those powers.