(Cross-posted at Official Google Blog)

As you know, the Democratic primary is coming down to the wire, and American voters are following each set of state results more closely than ever before.

We wondered what would make the difference in the tight Pennsylvania primary—and what those results might indicate about the rest of the primary process and the general election. So we turned to numbers-cruncher Jim Barnes from the National Journal and asked him to weigh in on different sets of demographic data. Jim helped us set up an embeddable Google Map comparing different essential factors for the Democratic primary in Pennsylvania.

As you’re watching the results from this race on April 22, there are five things to look for—and they have interesting implications for the general election in November:

Age. Barack Obama has generally drawn more support from younger voters while Hillary Clinton’s base has come from older voters. With 15.2 percent of its overall population aged 65 or older, Pennsylvania has the third biggest population of seniors in the country after Florida and West Virginia. The candidate who does a better job turning out this core age group could take a big step towards winning the primary. Take a look at the percentages of registered Democrats by age bracket.

Democratic primary in the 2002 gubernatorial race. In 2002, then-Pennsylvania State Auditor General Bob Casey Jr. lost the Democratic gubernatorial primary to then-Philadelphia mayor Ed Rendell, who went on to capture the statehouse. Casey carried 57 of the state’s 67 counties in that primary, but Rendell won the contest because of his strength in the southeastern part of the state, specifically the four suburban and exurban counties outside of Philadelphia—Bucks, Delaware, Chester and Montgomery—where he carried more that 80 percent of the vote. In the Democratic presidential race, Rendell has endorsed Clinton, and Casey is backing Obama. Whether Rendell can help Clinton hold down Obama’s margins in the Philadelphia area, where he is still popular, or Casey can give Obama a boost among his political base in western, central and northeastern Pennsylvania could be pivotal in this primary’s outcome. Here are county-by-county results for the 2002 Democratic primary for governor.

Geography and growth. Based on the results seven weeks ago for the primary next door in Ohio, Clinton should be favored in the Keystone State, but Pennsylvania is more diverse state in terms of its patterns of growth. It has rural and metropolitan areas that are losing population, and fast-growing exurbs. For Obama to do well, he must win not only in Philadelphia and Pittsburgh, but also in some of the faster-growing parts of the state. Track the rate of population growth in Pennsylvania counties from 2000-2007.

Race. Obama has had some difficulty winning a significant share of support from white voters in most of the 2008 Democratic presidential primaries, but at the same time he has dominated Clinton in regard to the African-American vote in these contests. Here is the racial breakdown of Pennsylvania's 67 counties.

Religion. Obama and Clinton recently participated in a forum on issues of faith that was held at Messiah College in Pennsylvania. So far in this primary season, Sen. Obama has done well among Democratic primary voters who identify as Protestants and other denominations, but lagged among Catholics. Review the data on religious adherence by county.

As technology continues to be an influential part of this race for President, we hope you can use this map to gain a better understanding about which factors are causing Pennsylvania citizens to cast their vote. Try using the data to make your own predictions for the Pennsylvania outcome, then check if you're right by following live results tonight on Google Maps.