Basic Facts Can Change Opinions

In the noisy, real policy world, where media coverage is not that attentive and people are not exposed to the same sources of information, you can't replicate a survey like this that has an introduction of a single, clean fact," Farkas said.

A postcard can introduce "a single, clean fact."

A Little Information Goes Long Way In Influencing Education Policy Opinions
from Miller-McCune Online Magazine:

Giving people basic facts changes their opinions on major schools issues — which may dismay those seeking more school funding.. . .

For several years, William Howell, a political science professor at the University of Chicago, and Martin West, an education professor at Brown University, have overseen an annual survey sponsored by the Program on Education Policy and Governance at Harvard University and Education Next, a journal from the conservative Hoover Institution, where West is an executive editor.
. . .
"If you can change 10 percent of the public's view on a particular issue by giving them a single fact, that's pretty striking," Howell said.