Sen. Mark Udall, Aisle-Crossing Advocate for the State of the Union Address

He's the son of a congressman who once ran for president, the nephew of a former Interior secretary, an outdoor athlete who has featured rock climbing in his political ads.

And Colorado Democratic Sen. Mark Udall is also the force behind the effort to mix up the seating at Tuesday's State of the Union address.

The push to work across the aisles is nothing new for Udall, who has made cooperating with others a theme of his campaigns. He began his political career as a state lawmaker in 1997 and, after a single two-year term, was narrowly elected to the U.S. House from Colorado's 2nd Congressional District. In 2008, he won his U.S. Senate seat.

So, who is this guy? Here's the lowdown:

The legacy: Mark's late father, Morris "Mo" Udall, represented part of Phoenix in the U.S. House from 1961 through 1991, and ran for president in 1976. (Disclosure: As a 17-year-old Iowan, I caucused for him.) Mark Udall's uncle (and Mo's brother), Stewart Udall, held the Arizona congressional seat before Mo did, giving it up to become Interior secretary for Presidents John F. Kennedy and Lyndon Johnson. Stewart Udall's son, Tom Udall, also serves in the U.S. Senate, representing New Mexico. Sen. Gordon Smith, a Republican from Oregon, is a cousin.

The Colorado connection: Before his political career began, Mo Udall played professional basketball in Denver for the Nuggets in the 1940s. There he met his eventual wife, Patricia "Sam" Udall, a native Coloradan. Mark says his mom, who won a cross-country women's flying competition in 1977, nurtured his love for . . .

The great outdoors: Before he turned to politics, Udall worked for Colorado Outward Bound for 20 years, first as a course director and later as executive director of the outdoor recreation school. Udall has climbed all of Colorado's 14,000-foot peaks, and he summited the world's third-highest peak, Kanchenjunga in Nepal's Himalayan region. Weather foiled his three attempts to climb Mount Everest. And rock climbing sometimes figures into his campaign ads. Udall lives just south of Boulder in Eldorado Springs, home of some of the country's most famous rock-climbing routes.

The humor. His father was known for his sense of humor, writing the memoir, "Too Funny to Be President." And Mark can occasionally crack wise too. In his 2008 Senate campaign, in which he was pummeled with attack ads, Udall began one of his ads by saying, "Quick! Lock your doors and hide! It's me, Mark Udall! I'm just kidding . . ." And Udall was the fifth congressman to brave Stephen Colbert's "Better Know a District," where he referred to the comedian as a "philosopher." "

The Tucson connection: Udall's reach across the aisle comes after the assassination attempt on Rep. Gabrielle Giffords outside a supermarket in her Tucson, Ariz., legislative district. Udall was born in Tucson and grew up in the nearby Oro Valley, just north of where the Giffords shooting occurred.

Maggie Fox: Udall's wife, an environmental lawyer, worked for the Sierra Club for 20 years, rising through the ranks to become deputy executive director. In 2006, she left to become president of America Votes, a progressive get-out-the-vote organization. In 2009 she became president and CEO of Alliance for Climate Action, founded by former Vice President Al Gore to educate and form coalitions on climate issues.

The policy: Udall has focused his efforts on energy and environmental issues. He gets low ratings from some conservative groups such as the National Taxpayers Union and the Club for Growth, and high ratings from groups such as Human Rights Watch and the League of Conservation Voters. Other groups, such as the National Rifle Association and the U.S. Chamber of Commerce, give him middling ratings.

The reach across the aisle: Udall has always emphasized working with Republicans. His ads for the 2008 Senate race repeatedly emphasized rising above partisan concerns. He even advocated "disagreeing without being disagreeable" on Colbert's show.

And who is Udall sitting with Tuesday night? Right now, his spokeswoman tells us to "stay tuned."