WASHINGTON—One evening in April 2008, three low-level staff members from the Obama presidential campaign—a baggage handler, a videographer and an advance man—gathered in the windowless basement of a Pennsylvania hotel for an improvised Passover Seder.

The day had been long, the hour was late, and the young men had not been home in months. So they had cadged some matzo and Manischewitz wine, hoping to create some semblance of the holiday.

Suddenly they heard a familiar voice. “;Hey, is this the Seder?”; Barack Obama asked, entering the room.

So begins the story of the Obama Seder, now one of the newest, most intimate and least likely of White House traditions. When Passover begins at sunset on Monday evening, Obama and about 20 others will gather for a ritual that neither the rabbinic sages nor the Founding Fathers would recognize.

In the Old Family Dining Room, under sparkling chandeliers and portraits of former first ladies, the mostly Jewish and African-American guests will recite prayers and retell the biblical story of slavery and liberation, ending with the traditional declaration “;Next year in Jerusalem.”; (Never mind the current chill in the administration's relationship with Israel.)

Top aides like David Axelrod and Valerie Jarrett will attend, but so will assistants like 24-year-old Herbie Ziskind. White House chefs will prepare Jewish participants' family recipes, even rendering chicken fat—better known as schmaltz—for just the right matzo ball flavor.

If last year is any guide, Malia and Sasha Obama will take on the duties of Jewish children, asking four questions about the night's purpose—along with a few of their own—and scrambling to find matzo hidden in the gleaming antique furniture.

That event was the first-ever presidential Seder, and also probably “;the first time in history that gefilte fish had been placed on White House dishware,”; said Eric Lesser, the former baggage handler, who organizes each year's ritual.

As in many Jewish households, the Obama Seder seems to take on new meaning each year, depending on what is happening in the world and in participants' lives (for this group, the former is often the same as the latter).

The first one took place at the bleakest point of the campaign, the long prelude to the Pennsylvania primary, which was dominated by a furor over Obama's former pastor. “;We were in the desert, so to speak,”; remembered Arun Chaudhary, then and now Obama's videographer, who grew up attending Seders with his half-Jewish, half-Indian family.

No one led the proceedings; everyone took turns reading aloud. Obama had brought Reggie Love, his personal aide, Jarrett and Eric Whitaker, another close friend, all African-American. Jennifer Psaki, the traveling press secretary, and Samantha Tubman, a press assistant, filtered in. Neither had ever been to a Seder, but they knew the Exodus story, Psaki from Catholic school and Tubman from childhood Sundays at black churches.

Together they peppered the outnumbered Jews at the table with questions, which the young men sometimes struggled to answer. “;We're not exactly crack Hebrew scholars,”; said Lesser, now an assistant to Axelrod.

Participants remember the evening as a rare moment of calm, an escape from the din of airplanes and rallies. As the tale of the Israelites unfolded, the campaign team half-jokingly identified with their plight—one day, they too would be free. At the close of the Seder, Obama added his own ending—“;Next year in the White House!”;

Indeed, the same group, with a few additions, has now made the Seder an Executive Mansion tradition. (No one ever considered inviting prominent rabbis or other Jewish leaders; it is a private event.)

But maintaining the original spirit has been easier said than done.

Tubman and Desiree Rogers, then the White House social secretary, tried to plan an informal meal last year, with little or even no wait staff required. White House ushers reacted with what seemed like polite horror. The president and the first lady simply do not serve themselves, they explained. The two sides negotiated a compromise: the gefilte fish would be pre-plated, the brisket passed family-style.

Then came what is now remembered as the Macaroon Security Standoff. At 6:30 p.m., with the Seder about to start, Neil Cohen, the husband of Michelle Obama's friend and adviser Susan Sher, was stuck at the gate bearing flourless cookies he had brought from Chicago. They were kosher for Passover, but not kosher with the Secret Service, which does not allow food into the building.

Offering to help, the president walked to the North Portico and peered out the door, startling tourists. He volunteered to go all the way to the gates, but advisers stopped him, fearing that would cause a ruckus. Everyone seemed momentarily befuddled. Could the commander in chief not summon a plate of cookies to his table? Finally, Love ran outside to clear them.

Obama began the Seder by invoking the universality of the holiday's themes of struggle and liberation. Malia and Sasha quickly found the hidden matzo and tucked it away again, so cleverly that Ziskind, the former advance man, needed 45 minutes to locate it. At the Seder's close, the group opened a door and sang to the prophet Elijah.

In preparation for this year's gathering, Lesser and others have again been collecting recipes from the guests, including matzo ball instructions from Patricia Winter, the mother of Melissa Winter, Michelle Obama's deputy chief of staff.

“;We like soft (not hard) matzo balls,”; Winter warned in a note to the White House chefs, instructing them to buy commercial mix but doctor it. Use three eggs, not two, she told them; substitute schmaltz for vegetable oil, and refrigerate them for a day before serving (but not in the soup).

The Seder originated with Jewish staff members on the campaign trail who could not go home, but now some celebrate at the White House by choice. Participants say their ties are practically familial by this point anyway. “;Some of the most challenging experiences of our life we've shared together,”; Jarrett said.

No one yet knows exactly what themes will emerge this year. Maybe “;taking care of people who can't take care of themselves and health care reform,”; suggested Sher, now Michelle Obama's chief of staff.

The evening might also reflect a group that has settled into the White House and a staff more familiar with the new custom. Last week, Sher was leaving the East Wing when a guard stopped her.

“;Hey, are you bringing macaroons again this year?”; he asked.