Two entrenched New York House incumbents, one from each party, could face tougher-than-usual re-election contests next year against youthful challengers.

Lawyer Kirsten Rutnik Gillibrand, a Democratic donor and activist, is preparing to take on Rep. John Sweeney (R) in the upstate 20th district. And in the 28th district, which extends from Buffalo to Rochester, Buffalo City Councilman Antoine Thompson (D) is expected to challenge Rep. Louise Slaughter in the Democratic primary.

Both Thompson and Gillibrand must be considered underdogs for now. But both represent a higher caliber of challenger than either incumbent is used to facing.

More significantly, their willingness to run illustrates the volatility in the Empire State’s once-stable Congressional delegation. Districts previously thought to be impenetrable now appear to be competitive, and with the state likely to lose two House seats in the next reapportionment, jockeying for future advantage is already well under way.

Of the two races, Thompson’s primary challenge to Slaughter may be the more intriguing.

At 35, Thompson is less than half the Congresswoman’s age; Slaughter turned 76 last month.

Thompson also is preparing to run at a time when black politicians in Buffalo are ascendant; state Sen. Byron Brown (D) is the frontrunner to become the city’s first black mayor in November’s open-seat race.

“I think we’re in for a very spirited contest,” said Joe Illuzzi, publisher of Politicswny.com, a Web site and monthly magazine on politics in Western New York. “Louise will have her hands full. There’s no question about it.”

In a phone interview this week, Thompson would not confirm that he is running.

“We’re thinking about it,” he said. “We’ll give it some careful consideration.”

But sources said Thompson is putting together fundraisers for a Congressional run and is telling acquaintances that he plans to raise $500,000 for the primary. He is scheduled to attend the Congressional Black Caucus Foundation’s legislative conference in Washington, D.C., later this week, where he is expected to huddle with party leaders.

Eric Burns, a spokesman for Slaughter, said the Congresswoman is focusing on her official duties these days.

“We’ve certainly heard the rumor [about Thompson], but it’s way too early to speculate about who’s running and who isn’t,” he said. “The one thing we know is Rep. Slaughter is running for re-election and that she is going to be re-elected.”

Slaughter, ranking member of the Rules Committee, was sitting on $390,000 in her campaign account as of June 30.

But while she has the advantages of 10 terms in Congress, Slaughter’s base has always been Rochester, and she’s still not terribly well known in the Buffalo portion of her district, which she picked up after redistricting in 2002. What’s more, minorities make up 38 percent of the district and probably an even bigger share of the Democratic primary vote.

Whether Thompson is trying to gain a leg up on other potential successors to Slaughter is hard to say. Slaughter shows no signs of slowing down, and it is widely expected that she will seek to stay in office at least until the next round of redistricting, when the Buffalo area could lose one of its three House seats.

Several other Western New York pols are considered possible successors to Slaughter whenever she decides to move on. They include state Assemblywoman Crystal Peoples (D), Assemblyman Sam Hoyt (D) and Lynn Marinelli (D), majority leader of the Erie County Legislature.

For Gillibrand, the numbers are somewhat more challenging. Sweeney represents a district that runs from the Hudson Valley, an hour or so outside of New York City, all the way north to the Adirondack Mountains. In 2004, President Bush bested Sen. John Kerry (D-Mass.) by 8 points there, and Sweeney hasn’t had to sweat any of his four elections.

Equally significant, Sweeney was sitting on a hefty $660,000 on June 30.

But Gillibrand is undaunted, saying Sweeney’s close ties to the House GOP leadership make him vulnerable.

“It is a 2-1 Republican district,” she conceded. “But I think that Republicans and Democrats and independents are feeling like they’re not getting the representation they deserve.”

While she has never run for office before, the 39-year-old lawyer is no political neophyte. She has been active in Democratic campaigns for years and has been a regular donor to Democratic candidates and causes. According to the Web site PoliticalMoneyLine.com, Gillibrand has made at least $23,000 in political donations to federal candidates and committees since the 2002 election cycle.

Gillibrand may find herself vulnerable to the charge that she is a carpetbagger, having lived and practiced law for the past several years in New York City. But she grew up in the 20th district, recently moved to the town of Hudson, and transferred to her law firm’s Albany office.

Gillibrand’s father, Douglas Rutnik, is a politically prominent lawyer and lobbyist in Albany who has been romantically linked, in published reports, with Zenia Mucha, the one-time top aide to New York Gov. George Pataki (R) and then-Sen. Alfonse D’Amato (R-N.Y.).

Gillibrand hasn’t formally announced her candidacy, but she is hosting the first fundraiser of her campaign on Friday in Albany and has a grass-roots event scheduled for Oct. 1 in Saratoga.

“We’re very excited” about Gillibrand, said Sarah Feinberg, a spokeswoman for the Democratic Congressional Campaign Committee. “She’s an excellent candidate.”

But whether Sweeney, a shrewd inside political player with close ties to Pataki and other state GOP leaders, can be vulnerable to a challenge from Gillibrand is an open question.

“Just because somebody wants to run doesn’t mean they’re going to be a good candidate,” said Carl Forti, communications director of the National Republican Congressional Committee.