In a country where many voters identify with a particular political party, "swing voters" -- those who do not have a strong party affiliation -- often take center stage in an election year.

Pundits and the media study swing voters closely while candidates target them with tailored campaign messages. Sometimes swing voters are thought of as a large group like this election year's much-discussed "NASCAR dads." Sometimes voters are considered part of a "swing" population because they are residents of a swing state, like Florida.

Who are these swing voters?
Roughly 30 percent of America's electorate is undecided, according to a recent Pew Research Center survey. Though most of these voters have expressed a preference for one particular party, they say they could still change their minds. Most of the swing voters are between the ages of 30 and 49, live in suburbs and have some college education, The Washington Post reported.

As expected, 39 percent of swing voters are independents, but 27 percent identify with Republicans and 25 percent as Democrats. Almost half of swing voters consider themselves moderates and a third as conservatives. The majority of swing voters, 55 percent, are women, according to the Pew Research Center survey.

According to the Pew study, swing voters agree with Democratic presidential candidate Sen. John Kerry of Massachusetts on economic matters, but side with President Bush on Iraq and the war on terrorism.

History of the swing voter
The "swing factor," according to the political newsletter, The Hotline, "is a statistical measure used in order to determine where and with which sub-group the race is unpredictable. From that, the term 'swing voters' was coined."

According to recent research conducted by Daron Shaw, PhD., an associate professor at the University of Texas, the election behavior of swing voters should be studied over a period of time. Shaw said that in order to understand the importance of a swing vote, people must realize how closely divided Americans are politically.

Using Reagan Democrats as the first notable example of swing voters, Shaw said the phenomenon grew from there.

Swing voters as groups
In recent years, each election has been marked with a group of swing voters -- 1992 was the year of the woman, 1994 -- the year of "angry white males," 1996 -- the soccer mom, and 2000 -- waitress moms.

According to Shaw, the swing voter becomes more legitimate when you can picture them as a group. The waitress moms, branded as blue-collared women who were typically single mothers, were an easy group for people to visualize -- Helen Hunt in "As Good as it Gets," a movie that came out only a year before the election.

Heading into this election year, a media buzz has surrounded one group in particular -- NASCAR dads -- a term used by Democratic consultant Celinda Lake in 2002 to describe white, conservative NASCAR fans.

Though the legitimacy of NASCAR dads as a swing vote is debated, in February President Bush, decked out in a racing jacket, flew on Air Force One to the Daytona 500, NASCAR's biggest annual event.

"Our message to them (NASCAR dads) is Democrats are not going to take away your guns, but Republicans are taking away your jobs," said Lake, the Democratic pollster, who worked as a consultant for the Clinton/Gore campaign.

Some pundits, however, have argued that NASCAR dads as a swing group is nothing more than hype.

"Having Democrats trolling for votes among NASCAR dads is like Republicans trolling for votes at a NOW (National Organization of Women) convention," said GOP pollster Whit Ayers, the Associated Press reported.

According to ABC News polling director, Gary Langer, there are only two true swing groups in America -- independents and white Catholics. According to Langer, if you win both of those groups you are likely to win the election.

"In our view, a swing voter group ought to fit two basic criteria -- its majority vote ought to swing between Democratic and Republican candidates from election to election; and it ought to be big enough to make a difference in the outcome," Langer said.

NASCAR dads, he argued, do not fit the criteria. After researching how rural, suburban, or small city married white men with children and incomes under $50,000 voted in 2000, he said they accounted for 2 percent of all voters, and supported George W. Bush over Al Gore, 70 to 27 percent.

Catholics and independents, however, have swung to both sides in past presidential elections. Ronald Reagan, George H.W. Bush and Bill Clinton all won the votes of Catholics and independents, subsequently winning their elections.

Swing states
Some political spectators argue that even more important than the swing voter is the swing state. According to Michael Dimock, research director at the Pew Center, there are at least 15 swing states -- Arkansas, Florida, Iowa, Louisiana, Michigan, Minnesota, Missouri, New Hampshire, New Mexico, Ohio, Oregon, Pennsylvania, Tennessee, West Virginia and Wisconsin.

The dynamics of the Electoral College makes swing states, and consequently swing voters in those states, critical to an election. The number of votes a state gets in the Electoral College is based on their representation in Congress -- the number of representatives they hold in the House, plus their two senators.

The popular vote usually determines which candidate receives all of one state's Electoral College votes. Therefore, the states with a high population of swing voters will be bombarded with campaign advertisements as candidates work toward collecting the 270 electoral votes needed to win out of 538 at stake.

-- By Sheryl Silverman, Online NewsHour