By Greg Botelho
(CNN) -- A presidential nominee may stand in as the party's representative in the race for the White House, but it's the platform that represents the party's ideals, views and priorities.
Anointing a presidential ticket and approving a platform are the two fundamental purposes of a party's national convention. Those two functions, the products of months of discussion and compromise, date back to the early 19th century and the first conventions.
"People tend to think of parties as conniving, corrupt and power-hungry, but the real reason parties formed was to get policies passed based on [party members'] common beliefs," said Marjorie Hershey, a political science professor at Indiana University. "A platform tries to portray these polices publicly ... and its purpose is the same now as it was at the beginning."
Nowadays, the climactic nomination process dominates the headlines and the platform takes a back seat. Its most rancorous debates typically occur far from the public eye; its convention role is limited to a few remarks and an orchestrated vote outside of prime time.
Party leaders craft the document to articulate generic beliefs and make policy distinctions with rival parties. After months of discussion and approval at the convention, the platform largely becomes an afterthought until its next incarnation four years later.
"The convention platforms are very important as an indication of where the parties stand, and they do contain very clear language," said Hershey, co-author of the college textbook "Party Politics in America," now in its 11th edition. "Platforms really do speak to the parties' differences on issues.
"But the platform's role is mostly as an expression of the party's values to itself, and it's not likely to make a difference in the campaign."
The platforms and presidential ticket are closely linked, with the nominee often working to shape the party's lengthy, judiciously worded mission statement. Conflicts can arise as the candidate shifts from currying the support of party activists -- who tend to hold more extreme positions than the mainstream -- during the primaries to reaching out to more centrist voters in the general election.
"All through the convention, the central factor is that basic tension -- that candidates need to appeal to centrist voters, but also keep the loyalty and rein in the passion of [a party's] more extreme groups," Hershey said.
The platform-building process begins about a year before the convention, months before primaries weed out other presidential contenders and produce a presumptive nominee. The national party chairman and state parties play a formative role, choosing a platform committee's members (186 for the Democrats this year) and defining the election season's key issues.
The platform committee, which includes a smaller drafting committee, conducts private and public meetings in the subsequent months, inviting fellow party members to testify on what issues they believe should be embraced in the final document.
The committee often reflects many of a party's core constituencies -- like labor, women's rights and minority groups in the case of the Democrats, and the Christian right, abortion-rights opponents and business organizations for Republicans -- as well as more moderate-minded activists.
When a candidate emerges from the primary field, his or her campaign team may try to shape the platform, typically trying to moderate its language so that it appeals more to centrist voters.
"Fights over the platform are internal fights over the party's policies, between [resolute] constituency groups and a candidate's desire to be more mainstream," Hershey said.
After the convention, a candidate may try to move away from the platform, as 1996 Republican nominee Bob Dole did when he said, "I probably agree with most everything in it, but I haven't read it."
In failing to do so, Dole saved himself hours of parsing nearly 28,000 words of general assertions, sharp arguments and harsh criticisms of then-President Bill Clinton.
Although few may read the full platform, each word is assiduously selected for its meaning and tone. In the past, delegates would debate individual tenets -- or "planks" -- of the platform on the convention floor.
But in recent decades, party leaders have curbed such extensive and potentially volatile debate -- a bid to keep to a strict schedule and avoid the appearance of internal dissent.
"What's going on is the presentation of a very carefully crafted image of their candidate," Hershey said. "The stakes are very high."
The platform's length, a presidential nominee's espousal of it (or lack thereof) and the fact that much of the debate happens behind the scenes do not diminish the strong, lucid language that often appears in the final draft.
Although a majority of a platform often consists of general, near-universal statements -- like asserting support for families, troops and the American spirit -- a sizable chunk usually spells out critical differences between the parties on hot-button issues such as abortion, gun control, economic policy and international affairs.
Candidates may not play up their party's platform on the campaign trail, but research shows that the winner ends up carrying out many platform planks, Hershey said.
In his presidential campaigns, consumer activist Ralph Nader has contended that the differences between Republicans and Democrats are minor, saying both parties are captive to corporate interests. Hershey dismisses Nader's contention.
"Ralph Nader's statements about the similarities between the parties are complete and utter nonsense," she said. "[Some people] think the Republicans and Democrats are all the same, just with two different faces. But there are very clear differences ... A look at the core of the platforms shows that."