This year's historic race for president is now down to its final days.

Between now and Election Day on November 4, Republicans, Democrats, political experts and the news media will be working overtime to determine whether John McCain or Barack Obama will win — and by how much.

To do this, they will be spending a lot of time looking at polls. Polls (pronounced POLES) are opinion surveys designed to find out what voters think about the candidates and issues.

They are especially important near the end of the campaign when candidates must decide what issues to emphasize and where to spend time campaigning in the race to the finish.

Polls ask voters questions created to find out how they will vote on Election Day.

Polls do not ask every voter the questions. Instead, a “sample“ is chosen of voters whose answers are believed to represent a larger group.

For polls to be reasonably accurate — and no poll is 100 percent right — the sample has to be chosen carefully to contain the same types of people that make up the larger group.

For example, a poll of your state’s voters should have roughly equal numbers of men and women, plus all the races and ethnic groups that live there.

People should be careful reading the results of any poll because poll results are like a snapshot taken with a camera. They show only what was happening at that moment. The results only tell what people in the sample felt on the day the poll was taken.

The results don’t last forever because people may change their minds. Or they may get more information that helps them make up their minds.

The size of the poll sample affects a poll’s accuracy. Usually, the larger the sample, the more accurate the poll. But there is always room for mistake — this is called “the margin of error.”

Every poll has a margin of error. A good poll may have a margin that is plus or minus 3 percentage points. With that margin, if the result says a candidate is liked by 50 percent of voters, you can be pretty sure that between 47 percent and 53 percent of voters like the candidate.

Because Barack Obama is the first African American nominated to be president, polls are getting extra attention this year from political experts and the press.

The reason is Tom Bradley.

In 1982, Bradley became the first African American nominated to be governor of California. Polls before the election said Bradley, the Democratic candidate, was winning by a comfortable margin. But when the state voted, he lost to Republican George Deukmejian.

Political experts trying to figure out why the polls were wrong said after the election that voters may have told pollsters they would be voting for Bradley but later voted against him because he was African American.

Polling experts don’t know if that is the reason Bradley appeared to be winning but lost. They also don’t know if that could happen this year with Obama. Experts will be watching election results closely to see how they match up to pre-election polling.