It's Back to Iowa, for Round 2

Not so fast, Pennsylvania. The next stop in the Democratic presidential race is ... Iowa.

Yes, Iowa.

Weeks before Pennsylvania holds its primary on April 22, states such as Iowa, Texas and Nevada will conduct the next round of voting in the multistep process of choosing delegates to the national convention this summer. Iowa, which first voted on Jan. 3, holds county conventions this weekend in familiar locales the candidates remember well, like Des Moines.

Welcome to the arcane world of the presidential caucus, where one day of voting is rarely enough to lock up national delegates and sometimes two rounds doesn't cut it, either. The party's system has both campaigns working to keep, and perhaps gain, delegates who have already been claimed in the early voting states.

At stake: 248 delegates in 10 states, more than enough to shift the balance of the entire race. The Associated Press has awarded 138 of those delegates to Sen. Barack Obama, who has fared well in caucus states. Ninety-six went to Sen. Hillary Rodham Clinton and 14 went to John Edwards, who has suspended his campaign.

Most years, the complexities of party caucuses don't generate much interest after the campaigns have moved on.

"This year, they will be fighting over every delegate," said Norm Sterzenbach, political director of the Iowa Democratic Party.

Obama leads Clinton in the race for national delegates, 1,602 to 1,496. But much of Obama's lead is built on delegates won in caucus states _ delegates who are not yet guaranteed to remain his. Here's why:

Most primaries and some caucuses are binding, meaning that national delegates won by the candidates must pledge to support them at the national convention this summer. Some high-profile caucuses, however, are just the beginning of a multilayer process of selecting delegates to the national convention in Denver in August.

In Iowa, precinct caucuses were held Jan. 3 to select delegates to county conventions this weekend. The county conventions will select delegates to congressional district conventions in April and the state convention in June.

National delegates are elected at the congressional district and state conventions _ the third step of the process. If all the delegates for each candidate show up at every step, the national delegates awarded Jan. 3 will remain unchanged.

But if one side is unable to rally its supporters at any step along the way, it risks losing national delegates.

Obama won the Iowa caucuses in January, picking up 16 national delegates. Clinton came in third, winning 15. Under Iowa's quirky system, Clinton won one more delegate than Edwards, even though Edwards got the second most votes.

Edwards' delegates _ and the chance to win them over _ will add intrigue to the Iowa conventions.

"Absolutely they're fair game," said Karen Hicks, a senior adviser to the Clinton campaign. "We are reaching out to a lot of them, trying to persuade them to join our team."

Both campaigns have been working behind the scenes in Iowa for several weeks, rallying supporters to attend the conventions on Saturday.

"We are doing what we can to make sure we hold onto all the Obama folks," said Obama campaign spokesman Bill Burton.

Iowa's caucus system is similar to those in other states, though there are critical differences.

In some states, like Colorado and Nevada, no national delegate is officially pledged to a presidential candidate at the initial caucuses. In other states, like Hawaii and Washington, some delegates are pledged at the initial caucuses, while others are not pledged until the state convention.

Other caucus states with delegates still in play are Alaska, Nebraska, North Dakota, Texas and Wyoming.

Iowa Democrats are preparing for big crowds on Saturday, which is probably a good idea after what happened at a county convention in Nevada last month.

The Clark County convention in Las Vegas devolved into chaos when a huge turnout overwhelmed party leaders and forced them to shut down the convention before completing the vote.

An estimated 10,000 people showed up for the convention, about 2,000 more than organizers expected. Rowdy crowds filled the ballroom to capacity and forced casino staff to close the doors early, leaving hundreds of delegates outside.

After conferring with the campaigns, party leaders rescheduled the convention for April 12, when they plan to extend voting over 11 hours to keep the crowds down.

"It's something that Nevada had never seen before," said Kirsten Searer, a spokeswoman for the Nevada Democrats. "In a lot of ways it's a good problem to have because, obviously, people are connected to these candidates. But it's hard to plan for something like this."

(This version CORRECTS UPDATES with new delegates; DELETES INcorrect reference to Kansas, and adjusts delegates at stake; ADDS photos)