Candidates for the American presidency are selected by a process that is rigid and unfair. Might that be about to change?

In 2004, the US presidential primaries offered little excitement. Incumbent George W. Bush was the Republicans' obvious choice, and the Democratic nomination process effectively ended with Massachusetts Senator John Kerry's victory in the Iowa caucus - an early win that led his party to coalesce quickly around him. But the 2008 primary will be much different. Both nominations are wide open because, for the first time in half a century, neither side has a sitting president or vice president in the race. As many as two dozen candidates may run. And this means that the state-level contests to pick the nominees promise to be more important and exciting than ever.

Given this newfound relevance, it's not surprising that several states are, in the hopes of exercising greater influence over the process, trying to change the dates on which their primaries are held. Democrats in four of the most populous states in the country - California, Florida, Illinois and New Jersey - recently signaled that they want to hold their primaries earlier in the campaign. Since the early states determine which candidates have the momentum - snowballs are hard to stop when they start down the mountain - the potential for change is huge.

Any serious reordering of the calendar will affect who gets nominated. And the immediate effect of any change, no matter the states involved, would be a reduction in the influence of Iowa and New Hampshire, which traditionally render the first judgments. Though they will try to retain their primacy, a shift that pushes other states forward is likely to diminish the two states' disproportionate influence. Iowa and New Hampshire are small states with small populations. In fact, the seven most-populous counties in California each contain more citizens than all of New Hampshire; geographically, one California county is twice the size of the tiny state.

Then there's the question of money. If large states as far apart as California and Florida do push their primaries earlier, the need for candidates to reach lots of voters across long distances will require that they have large amounts of cash on hand. Only the most well-financed contenders, such as Hillary Clinton and John McCain, will be able to purchase the television time and manpower necessary to compete.

And all the states hoping to leap-frog their way to an earlier calendar date have populations that are far more diverse than those of Iowa and New Hampshire. All four have double-digit Hispanics populations, and major cities like Los Angeles, Miami, Newark and Chicago feature high concentrations of African-American voters. Both minority groups could prove pivotal in the Democratic primary - in stark contrast to past races, where the mostly-white states of New Hampshire and Iowa practically determined the nominees.

In the Republican primaries, particular candidates will gain an edge from the potential shift. The percentage of evangelicals or born-again Christians in the four states - California, 17%; Florida, 23%; Illinois, 20%; New Jersey, 8% - is smaller than in Iowa, where three in ten voters are self-described evangelicals. As a key voting bloc in the Republican Party, evangelical Christians tend to favour candidates like Kansas Senator Sam Brownback, who is highly conservative on issues like abortion and gay marriage. But if the evangelical influence declines, social liberals like former New York City Mayor Rudy Giuliani stand to gain.

But the most interesting potential effect of a change in the primary calendar is that it will force candidates to compete in a greater number of states: of the four in question, three were not competitive in the last two presidential elections - they swung unambiguously to one candidate or the other. As a result, the 2000 and 2004 presidential elections produced the most stable back-to-back results in American history, with just three states switching from one party to the other. Many of the stable states were simply ignored.

The growing frustration of partisans in these states is palpable. And given that the four large states now angling for a greater role account for 44% of the total electoral vote, their frustrations seem more legitimate than ever.