Sometimes politicians are hampered by the fact that the public may desire legislation that is unconstitutional or not feasible, but politicians do seem to strive towards making the public happy. Moreover, when there is a negative downturn in a party or president's popularity, the politicians seem especially likely to respond. "Negative public opinion can have a powerful impact on policymaking. Low standing in the polls may encourage a president to drop an unpopular proposal or to promote new, supposedly more popular proposals" (Manza & Cook, 2002). In fact, when investigating the empirical evidence, it appears that public opinion does shape policy. Erikson, Mackuen, and Stimson examined the question of whether the government responds to changes in public opinion and their answer was an "unqualified 'Yes'" (2002). In fact, they found that "Mood affects policy activity two ways" (Erikson, Mackuen, & Stimson, 2002). First, public opinion changes which party is in power, because Democrats are perceived to be more liberal than Republicans, and "the electorate chooses the party composition based on its current mood" (Erikson, Mackuen, & Stimson, 2002). Furthermore, politicians, once elected, act in a way to avoid sanctions by the voters, so that, if there is a mood shift after an election, politicians may not act in a way reflecting their parties' traditional stances.

While it is clear that public opinion can help shape public policy, it is important...

"Liberal policy breeds conservative mood and vice versa because popular liberal legislation lessens the perceived need for more liberal legislation and popular conservative legislation lessens the perceived need for more conservative legislation" (Erikson, Mackuen, & Stimson, 2002). In fact, public opinion polls do not demonstrate absolute mood, but rather reflect the relative mood of the public. Therefore, while public opinion shapes policy, policy also shapes opinion. As a whole, the American electorate is moderate, with shifts towards liberalism or conservatism in response to governmental actions. Therefore, even when the public seems happy with changes, if the government shifts too far to the left or the right, one can expect a swing in the other direction by the electorate.
References

Erikson, R., Mackuen, M. & Stimson, J. (2002). Public opinion and policy: Causal flow in a macro system mode. In J. Manza, F. Cook, and B. Page (Eds.), Navigating public opinion: polls, policy, and the future of American Democracy (pp.33-53). New York: Oxford University Press.

Manza, J. & Cook, F. (2002). The impact of public opinion on public policy: The state of the debate. In J. Manza, F. Cook, and B. Page (Eds.), Navigating public opinion: polls, policy, and the future of American Democracy (pp.17-32). New York: Oxford University Press.