Every presidential aspirant uses opinion polling data to shape his or her campaign in the quest for the White House. In this segment of How America Elects, VOA's Jeffrey Young looks at the vital role of polls and pollsters in forging campaign strategies.

Who leads the race to the White House? What are the big issues voters care about? Political candidates and their parties get those answers from public opinion polling.

Political campaigns use polls to make critical strategy and resource decisions -- everything from where the candidate needs to make personal appearances to which campaign issues resonate with voters.

The Gallup Organization has conducted political polling since the 1930s. Gallup official Frank Newport says these surveys serve as blueprints. "Candidates today, or political parties, use polling to set the framework, to actually design their campaign," he explains. "Oftentimes, they will look to see what issues they should emphasize and what issues they shouldn't emphasize in their overall strategy. Then, campaigns and candidates and parties use the polling as a benchmark as the campaign continues to know how they're doing." 

Polls, like blueprints, must be accurate. That requires carefully constructing survey sample groups using proven formulas and principles. Zogby International's Michelle van Gilder explains, "It's all done through mathematical equations and rules of probability. You can get a sample that some may consider [to be] relatively modest if you are looking at a country with the [300 million] population of the United States -- of 1,000. But with that 1,000 [person sample size], which most pollsters use for your typical polls, that will give you a very high level of accuracy."

Major U.S. pollsters such as Zogby and Gallup operate telephone survey centers to reach the people selected to be in their sample groups. Only a small amount of this polling is done face-to-face, or over the Internet.

By asking a number of questions, pollsters get a sense of how each candidate's stance on significant election issues is supported by voters.

Polling also provides political parties with trends, such as how favorably voters view the Republicans versus the Democrats over a span of time.

But Frank Newport at Gallup says that candidates can also over-react to polling data, and by doing that, risk losing some of their support. "Some people criticize candidates if they go too far in changing their positions just to meet what polling shows what the public wants. So candidates have to be careful in how far they move in that direction," he said. 

Between now and election day scores of polls will be conducted, prompting endless analysis by both the campaigns and those who observe politics. But ultimately, the only poll that matters is the ballot box itself.