Filmmaker Mary Lambert’s latest project “14 Women,” which follows the lives of the female Senators who served during the 109th Congress, likely wouldn’t have come about without a little assistance from a well-placed family member.

That’s because the 55-year-old, director of numerous feature films and iconic music videos, including Madonna’s “Material Girl” and “Like a Prayer,” just happens to be Sen. Blanche Lincoln’s (D-Ark.) big sis.

“I began to look at the videos and pictures I’d taken of Blanche and [realized] she was really part of a whole new world … to which I had unique access,” Lambert recalled.

By the spring of 2004, Lambert had begun the documentary in earnest at the urging of her longtime friend and business partner Sharon Oreck, a co-producer on the film (the result debuts Thursday night as part of the Silverdocs Film Festival at the AFI Silver Theatre). Then, at that year’s Democratic National Convention, Lambert struck up a conversation with TV and film producer Nicole Boxer, daughter of Sen. Barbara Boxer (D-Calif.) and ex-sister-in-law of Sen. Hillary Rodham Clinton (D-N.Y.), who soon signed on as a producer.

Even with the all those familial ties, getting all 14 women on board was hardly assured.

“We weren’t immediately embraced by everyone,” Lambert conceded. “I had to convince them I wanted to make a film that was bipartisan, that presented everyone in a clear light.”

And there were moments when even Lambert’s sister got tired of the intrusion.

“She would be like, ‘Please turn the cameras off, please get out of my house,’” Lambert laughs.

As for the most difficult woman to nail down?

Definitely Clinton, said Nicole Boxer, who also appears in the film. Given scheduling difficulties, the Democratic presidential hopeful’s interview was “outsourced” to Lambert’s husband, Jerome Gary — producer of “Pumping Iron” — and of all the Senators she appears the most scripted. (“It’s a very difficult job,” Clinton says of being a Senator, in a representative snippet from the film. “There’s a lot of slings and arrows.”)

So how did Lambert and Boxer, two self-avowed Democrats, strike up a rapport with some of their Republican subjects?

“There’s something to admire and respect about each woman,” Lambert said, noting that she occasionally parted ways with her own sister on politics. “I don’t always agree with all of Blanche’s decisions.”

That’s not to say party IDs didn’t take some overcoming.

Boxer, who interviewed 12 of the 14 female Senators, said one of the most difficult moments came when she headed to the Lone Star State to capture Sen. Kay Bailey Hutchison (R-Texas) at the GOP state convention. “I thought, ‘Oh my God, if they just knew who I was,’” Boxer said, comparing the experience to “walking into the belly of the beast.”

“I saw T-shirts criticizing my mom,” she added, acknowledging that Sen. Boxer is often viewed as the “poster child for liberals.”

For Boxer, who was 15 when her mother first ran for Congress and once served as a page to then-Rep. Joe Moakley (D-Mass.), the project marked a return to her roots. “Some of these women I remember from when I was a page,” she noted, referring to Sens. Barbara Mikulski (D-Md.) and Olympia Snowe (R-Maine), who were serving in the House at the time.

While Boxer, 39, is quick to admit “there’s a lot of subjectivity” to the film, its pro-girl, pro-parity message is unlikely to ruffle many feathers. The same can’t be said of its funding. The filmmakers have garnered some flak in the press for taking a $150,000 grant for the project from Wal-Mart, which has been the target of criticism for its labor policies, including its treatment of female employees.

Lambert and Boxer defended the decision to take money from the Bentonville, Ark.-based company. “There wasn’t any big liberal group out there that wanted to make” the film, Lambert said, adding that she had complete artistic freedom. (Earlier this spring, Wal-Mart hosted a Capitol Hill reception for the female Senators in honor of the film.)

“I give Wal-Mart credit for trying to do better,” said Boxer, who lives on Capitol Hill with her mom and son Zach Rodham (nephew of Clinton), and considers herself “a Whole Foods person.” “To be honest, I have never shopped at Wal-Mart in my life. I grew up in a place where Wal-Mart didn’t exist. … [It’s] not part of my consciousness.”

Narrated by Annette Bening, the 79-minute film shows the female Senators at work in the Capitol, on the road in their home states, on the campaign trail and even in their family kitchen.

There are a few genuinely riveting moments. For instance, Sen. Dianne Feinstein (D-Calif.) describes the scene in the San Francisco city hall the day in 1978 when both Mayor George Moscone and gay Supervisor Harvey Milk were shot dead by disgruntled rival politician Dan White. I “tried to get a pulse. Put my fingers through a bullet hole,” recalls Feinstein, who as the then-president of the Board of Supervisors assumed the mayorship in the wake of the killings. She goes on to attribute her political centrism to the challenges of governing San Francisco amid such volatility. Meanwhile, Snowe points to the death of her first husband in a car accident as having “inspired” her to get involved in public life.

Unfortunately, such moments are more the exception. More standard are scenes such as Sen. Lisa Murkowski (R-Alaska) eating dinner with her husband and two boys, neither of whom seem too keen on having had to move to the Washington, D.C., area. Or Sen. Boxer shopping at the Eastern Market meat counter after a press conference. Or Lincoln chatting with her sick child via cell phone while her car speeds through an Arkansas landscape. Life may be composed mainly of the ordinary, but it’s not always that riveting to watch.

Aside from the footage of the 14 female Senators and an epilogue that touches on the 2006 election of two additional female Senators, Amy Klobuchar (D-Minn.) and Claire McCaskill (D-Mo.), some inclusions feel haphazard.

Rocker Alanis Morissette is seen playing for a Boxer fundraiser and later shows up weighing in on women and power. Periodically, a group of Los Angeles-area seventh- and eighth-grade girls appear on screen to share their views on the Senate and women in politics. (One girl thinks the president picks Senators; another has no idea what a Senator is.) Only one male Senator is interviewed — Sen. Joseph Biden (D-Del.), who talks about the importance of getting women on the Judiciary Committee after the Anita Hill hearings — which leaves the project feeling a bit unbalanced, a fault that Lambert seems aware of.

“I really regret we didn’t pursue Sen. [Trent] Lott [R-Miss.] or one of the more conservative Senators for their point of view. … We kind of ran out of time. I [came] very close to just saying we stop everything. We are going to get Sen. [John] McCain [R-Ariz.] one way or the other,” she said. “Maybe the sequel.”

“14 Women” debuts at 7 p.m. Thursday at the 2007 Silverdocs Film Festival at the AFI Silver Theatre. For more information, visit www.silverdocs.com.