The narrowed U.S. presidential race will enter a new phase when voters in more than 20 states hold primaries and caucuses Tuesday. But political experts say that for the Democratic Party, rules on counting delegates will make it difficult for either Hillary Clinton or Barack Obama to emerge as a decisive victor for some time. VOA's Leta Hong Fincher has more.

Before the 1988 convention, the Democratic Party had a "winner-take-all" system of counting votes in the primaries. Michael Dukakis defeated Jesse Jackson to win the nomination, but Jackson asked that party rules be changed to allow candidates to win delegates regardless of who comes first in each state.

Political observers say that Democratic Party rule could face its first real test in 20 years, as Senator Barack Obama and Senator Hillary Clinton are locked in a tight race that makes it difficult for either candidate to pull ahead.

"[In] the Republican process, somebody, most likely McCain, will pull way ahead and the other challengers simply will not be in a position to catch him. That's not going to happen in our [Democratic] party. We're going to have a close contest that proceeds probably through the month of February, into early March," says Tad Devine, who is a Democratic Party strategist unaffiliated with a campaign.

Devine negotiated the Democratic Party rules in 1988 on behalf of the Dukakis campaign. Proportional representation rules split the delegates between the two Democratic Party candidates who are able to achieve 30 percent or more of the vote.

"Proportional representation presents a challenge accumulating delegates when you have two candidates [Clinton and Obama] who are well funded, who have broad political support, who have support with divergent groups of voters," he said.

The Republican Party, by contrast, has a number of states with a winner-take-all system.

In Florida's recent primary, for example, Senator John McCain won with 36 percent of the popular vote and picked up all of the state's delegates. Former Massachusetts Governor Mitt Romney won 31 percent of the vote but no delegates.

On the Democratic side, Clinton won with 50 percent of the Florida vote, followed by Obama with 33 percent. But Clinton received no delegates because the state held its primary earlier than allowed by the Democratic National Committee.

Political observers admit that the difference in how both parties set their rules can lead to some confusion.

"The big reason it's messy is because we don't have a very centralized system of having elections, even these primary elections for the parties," says John Fortier, an elections expert at the conservative American Enterprise Institute in Washington. "The national parties try to set some rules, but the state parties have a lot of leeway as to what they do. The only real punishment the national party can mete out to its state parties if they break the rules is to say we're not going to count your results in the convention, we're not going to seat the delegates."

Already, Clinton and Obama are in a dispute over whether the Florida results should be counted at the Democratic Party convention. Clinton wants to have the Florida delegates seated. Obama says the results should not count because the candidates agreed not to campaign there.