A narrow victory in this week's congressional race in Republican-leaning South Dakota has Democrats talking of something that seemed unthinkable six months ago: the possibility of regaining the House majority this fall after a decade in the minority.

Even the most optimistic Democrats agree that it is an uphill fight, but Stephanie Herseth's win in Tuesday's special election lends credence to claims that the party can grab seats from the GOP in districts carried by President Bush in 2000 if it runs smart, strong candidates. Democratic leaders said yesterday that several such campaigns are underway nationwide.

Gaining the House majority on Nov. 2 "is more than possible," said Rep. Robert T. Matsui Calif.), chairman of the Democratic Congressional Campaign Committee. "I think we have a very good shot at it."

Republicans scoffed at the idea, noting that they hold a dozen-seat cushion and are well positioned to knock off several Democrats in Texas alone. Still, GOP leaders seemed on the defensive, having to explain away their second special-election loss within four months in a district previously held by a Republican.

Herseth, 33, a member of a prominent political family in South Dakota, took 51 percent of the vote against Republican Larry Diedrich in Tuesday's election to replace William J. Janklow (R), who resigned after his role in a fatal auto accident. Herseth entered the special election with name recognition, having narrowly lost the 2002 House race to Janklow. South Dakota has only one House member.

Republicans yesterday cited the slow start by Diedrich, a former state senator, and portrayed his loss as a psychological victory.

"Three months ago he was down 30 points [in a poll], and he brought it to within a percentage point" on Election Day, said House Majority Leader Tom DeLay (R-Tex.). He predicted Diedrich will oust Herseth in November, when the two will face each other again, this time for a full two-year term. "I don't think the Democrats have a whole lot to crow about," DeLay told reporters.

But Democrats could hardly hide their joy, noting that Republicans had sent first lady Laura Bush, Vice President Cheney and Speaker J. Dennis Hastert (R-Ill.) to campaign for Diedrich. They likened Herseth's win to the Feb. 17 special-election victory in Kentucky of Rep. A.B. "Ben" Chandler (D), who handily won a previously Republican-held seat against a GOP nominee who had tied herself closely to Bush.

The Chandler and Herseth victories in states that Bush had easily carried in 2000, Matsui said in an interview, "really indicate that there's a national trend of people wanting change."

DeLay and other Republicans said both elections turned on local, not national, issues.

Republicans now hold 228 House seats to the Democrats' 206 (there is one independent). Democrats technically must net 11 new seats this fall to gain the majority, although the realistic number is 12 because they are not contesting a redistricted Texas seat now held by a Democrat.

That goal would be within reach, if events break their way, party leaders say. They feel poised to pick up the seats being vacated by GOP Reps. Jennifer Dunn (Wash.), Jack Quinn (N.Y.) and W.J. "Billy" Tauzin (La.). And they hope to knock off Republicans in Connecticut, Colorado, Nevada, New Jersey, Georgia and elsewhere.

Republicans say they will successfully defend most or all of those seats. Meanwhile, in Texas, an aggressive Republican redistricting plan has put five Democratic House members in danger.

"Democrats have a right to feel good today," Amy Walter of the independent Cook Political Report said yesterday. "But I'd be wary of reading too much into it." Noting that Democrats say they are poised to capture a political breeze and sail to victory in November, Walter said: "You need not just a breeze; you need a hurricane."