The legendary director Robert Altman is coming to Washington next week to tout his upcoming television mockumentary “Tanner on Tanner,” which is chock full of cameos by Democratic politicians, strategists and pundits. The series, which will air on the Sundance Channel, is a sequel of sorts to “Tanner ’88,” the 1988 series by Altman and Garry Trudeau that features a little-known Democratic Congressman named Jack Tanner who runs for president (and loses).

Now, 16 years later (and in the hideous era of reality TV) “Tanner on Tanner” features Alex Tanner, played by Cynthia Nixon of “Sex and the City,” making a documentary on presidential politics as seen through the eyes of her father, Jack, who’s played by Michael Murphy. After the film lands with a thud, Alex races to the 2004 Democratic National Convention to salvage her documentary, called “My Candidate,” by interviewing other presidential also-rans.

This is where the cameos come in.

The character Alex Tanner interviews everyone from TV shouter Chris Matthews and former New York Gov. Mario Cuomo to presidential hopeful John Kerry’s (D) daughter Alex and failed presidential candidates Howard Dean and Richard Gephardt. Former White House Chief of Staff John Podesta and former Secretary of State Madeleine Albright also make appearances.

Adam Pincus, the executive producer of the project, calls the technique “truly unique — its own animal.” He calls it a “hybrid of fiction and reality — not a reality in any way, not really a mockumentary, either.”

“Altman is a genius, whether he’s doing film or television,” Pincus added effusively.

Altman and his team will be visiting major media organizations, including Roll Call, next week.

Poop Scoop. Folks on the third floor of the Senate were complaining on Wednesday that it smelled really yucky up there. Like doo-doo, specifically. “It smells like s–t,” one source said. Another, more demurely, called it “sewage.”

That source says the stench began on Monday and got progressively worse as the week wore on.

Everyone was convinced that construction workers had hit a sewage line. The Architect of the Capitol’s office prefers to call it “a water leak.”

Eva Malecki, a communications officer for the Architect’s office, acknowledged there “may be sewage in that water.” But she said officials had not identified the source of the leak — and they weren’t sure yet whether the stinky situation was caused by the ongoing construction around the Capitol.

The Architect’s office shut off the air in parts of the Senate wing Wednesday “because there was a slight odor coming in,” Malecki said.

The next step, she added, would be to sanitize the air shafts with cleaning solution. So, all ye who smelt it, expect to inhale cleaning fumes today, rather than sewage.

“We’d prefer that,” a source on the third floor of the Senate assured us.

Hello Kitty. Kitty Kelley’s book party Monday night — celebrating the publication of her latest volume trashing the Bush family — was notable for its lack of luminaries. Indeed, the most noticeable figures were a mixed bag of Washington attention-seekers and whistleblowers.

Among them: former Ambassador Joe Wilson and Valerie Plame, who was outed as a spy by conservative columnist Bob Novak (surprise surprise, he was not at the party); Sidney Blumenthal, editor in chief of the liberal Salon magazine; writer and activist Andrew Sullivan; Mike Rogers, the gay gay-outer; Betty Currie, former President Bill Clinton’s White House secretary; former Clinton attorney Abbe Lowell; and Lynn Bernabei, resident lawyer for whistleblowers.

The event took place at the Warner Atrium, which, with its bad acoustics and impersonal open space, gives the feel of a shopping mall or a convention center. As one guest put it, “I feel like I’m in Houston.”

Tennessee. An HOH source walking down the long hallway that connects the Cannon and Longworth House office buildings to the Capitol noticed an error on a wall featurinig artwork from different states: Tennessee is misspelled. “Can we [get] the spelling correct?” the tipster pleads. “With [Senate Majority Leader Bill] Frist and [Sen. Lamar] Alexander on the Health, Education, Labor and Pensions Committee, the Capitol should get this right.”

Cub Reporter. The Fourth Estate just got a lot cuter. Roll Call’s very own intrepid reporter Mark Preston, who covers the Senate, and his wife, Meredith Preston, a reporter for BNA, are the proud parents of (we’re told) a beautiful baby girl.

Catherine Ray Preston was born Wednesday at 3 p.m. in Washington, weighing in at a classy 6 pounds, 15 ounces. She is the Prestons’ first child.

In an interview with the proud papa, HOH asked if Catherine really looked more like a shriveled-up raisin, as often happens to newborns. “Oh, no. She really is pretty. Seriously. Even the doctor was like, ‘Oh look at that skin,’” Preston said.

“She’s gonna break hearts,” he added, letting out the first sigh of what we’re sure will be a wonderfully challenging and immensely fulfilling fatherhood.

Little Catherine took a few days to be born, which the Prestons say either means she has the patience of her mother or the stubbornness of her father. HOH and everyone else at Roll Call is hoping the baby has more of mom’s genes.

Sen. Lincoln Chafee (R-R.I.), who congratulated Mark and Meredith on the floor of the Senate after learning of their marriage in 2000, predicted, with some nervousness, that they would one day sire “reporter babies.”

“No,” Mark Preston insisted in an interview from Meredith’s hospital room. “She’s going to be a successful businesswoman.”

Please send your hot tips, juicy gossip or comments to hoh@rollcall.com.