Economist David Friedman has an excellent post on the power of political labeling to influence opinion:
A well chosen name wins an argument by assuming its conclusion. Label cash subsidies to foreign government as "foreign aid" and who can be so hard hearted as to oppose them. Call subsidies to the public schools "aid to education" and you neatly skip over the question of whether additional spending in the public school system results in more education. Label something "pollution" and is no longer necessary to offer evidence that it is bad, since everyone knows pollution is bad—even thermal pollution, otherwise described as warm water. Occasionally we even get dueling names. Both "right to life" and "pro-choice" are obviously good things; how could anyone be against either?
For a more recent example, consider Obama's economic policy. Everyone—including Obama, back when he was running for President—is against deficit spending. Relabel it "stimulus" and everyone is for it. The label neatly evades the question of whether having the government borrow money and spend it is actually a way of getting out of a recession—a claim for which evidence is distinctly thin. It is stimulus, so obviously it must stimulate.
Friedman's list of rhetorical manipulations can easily be extended. For example, polls show that whether the public supports or opposes race-conscious policies that seek to aid minorities depends crucially on whether they are described as "affirmative action" (which gets strong majority support) or "racial preferences" (a term that triggers overwhelming opposition). Conservative activists use rhetorical ploys to build support for their positions no less than liberal ones do. For example, they label critics of harsh sentencing guidelines as "soft on crime," even though the point at issue is precisely whether these laws really do reduce crime better than alternative policies would.
Why is such rhetorical manipulation effective? If voters were well-informed about the details of public policy, clever labeling would be unlikely to sway them. If you have a well-informed opinion about affirmative action or Obama's stimulus plan, you probably won't change your mind merely because of a change in terminology.
In reality, however, most citizens know very little about politics and public policy, and it is perfectly "rational" behavior for them to remain largely ignorant. As a result, they can be swayed by rhetorical ploys such as the ones described by Friedman. That, in turn, explains why politicians and activists expend so much effort manipulating voter ignorance by cloaking their policies in attractive rhetoric, and making those labels stick in the public mind. Often, the side with the better rhetoric or more easily packaged programs will prevail over the side with the better, but more difficult to label policies.