Democratic hopes of regaining the Senate majority hinge first on defending five endangered seats, with none more important than that of Minority Leader Thomas A. Daschle. Daschle, long a fixture of South Dakota politics, is holding on by a thread as Republicans spend millions to try to protect their thin majority and topple a high-profile nemesis. Democrats have spent even more, making this lightly populated prairie state the unlikely epicenter of a battle for control of the Senate.

"This is South Dakota's time," Daschle said at a recent rally in this Missouri River town, where he asked for help in holding off Republican John Thune. Indeed, South Dakota's approximately 750,000 residents are poised to prove whether a Democrat from a state solidly Republican at the presidential level can lead his party in Washington while placating voters back home. Polls have shown Daschle with a tiny lead, but activists in both parties predict an election night nail-biter.

With Republican senators retiring in Oklahoma and Colorado and a third battling for her seat in Alaska, Democrats have a chance to pick up three seats on Nov. 2. That would be enough to control the chamber, where there are 51 Republicans, 48 Democrats and one independent who sides with the Democrats. But Democrats still would have to retain three or four of their five threatened seats to prevail.

Those are huge ifs. In addition to Daschle's all-out battle, Democrats are trying to hold seats left open by retirements in three states that President Bush is virtually certain to carry -- North Carolina, South Carolina and Louisiana -- and in the toss-up state of Florida. Georgia is considered unwinnable, but Democrats are positioned to grab Illinois's GOP-held seat, so they would offset each other.

With Bush favored to carry seven of the eight states with highly competitive Senate races -- and Florida considered a dead heat -- Democratic nominees are focusing on local and nonpartisan issues as much as possible.

Daschle, for example, almost never mentions the parliamentary maneuvering and coalition-building central to his leadership job in Washington. Instead, he repeatedly airs 30-second TV ads that portray him as a master of pork -- the man who procures bridges, highway bypasses and water projects with federal money.

"In my lifetime, I can't remember anyone else who did more for South Dakota than Tom Daschle," retired farmer Pat Lyons, 76, said at the senator's Yankton rally, which featured barbecue sandwiches and beans.

Thune is a former House member who lost the 2002 Senate race to Tim Johnson (D) by 524 votes. His backers have countered with their own ad avalanche, contending Daschle pushes a liberal agenda in Washington that he hides from constituents. Those ads resonate with Dennis Kaufman, 40, who manages computer data for a Sioux Falls health care firm.

"Daschle has been powerful, and that has been an asset to the state," he said during a recent lunch break with two co-workers. "But I feel he no longer represents the state, the small-town beliefs of the state."

Ads for and against the two nominees flood the commercial breaks of every local newscast and scores of other TV programs night and day, to the point that some voters say they stopped listening months ago. Through Sept. 30, Daschle had raised $18.3 million to Thune's $12.8 million, much of it going to the ad wars.

Conservative groups including the Club for Growth and U.S. Chamber of Commerce have spent millions more on ads attacking Daschle on tax and civil litigation issues. The three-term senator has barred outside groups from running ads on his behalf, but he is airing his own 30-second attacks. One features voters saying that Thune "gets pushed around by Wall Street and the big boys in Washington," and that "Daschle cuts taxes for the middle class; Thune cuts taxes for the rich."

The candidates sparred in two televised debates late last week, but more local headlines have gone to the resignations of six GOP staff members who helped college students apply for absentee ballots without proper notarization.

Ultimately the campaign may turn on whether voters believe that Daschle's role in securing federal drought aid, highway funding and subsidies for corn-based ethanol is enough to justify a fourth term.

Kelly Skoglund, 36, a construction worker who lunched this week at Emily's Cafe in Beresford, acknowledged the "power that Daschle has" in Washington. He added, however, "I don't know what he's done so far" to help people such as himself. "Why isn't Daschle working with senators from other states" to export more South Dakota-produced ethanol?

Such comments worry Daschle supporters, including lawyer Casey Davidson, 49, of Vermillion. A tiny state such as South Dakota, he said, cannot afford to dump a party leader, even if he is less conservative than the average voter. "When you have a senior member of Congress," he said, "who cares if you disagree with him?"

Nationwide, 34 Senate seats are at stake, more than two-thirds of them safe for incumbents. Political analysts say eight races remain tossups -- four in the South and four in the West and Midwest. Only two of the races involve incumbents.

This is in stark contrast with the outlook a year ago when the chief suspense was over the size of the likely Republican gain. But Democrats recruited strong candidates for key races, beefed up fundraising operations and pushed themselves to within striking distance of winning a Senate majority.

Jennifer Duffy, who watches Senate races for the independent Cook Political Report, gives Republicans a 70 percent chance of retaining their majority, and some analysts predict a GOP pickup of one or two seats. They note that Democrats are bucking a pro-Bush tide in most of the key Senate races.

Republicans are trying to capitalize by linking Democratic nominees to anti-Bush rhetoric even in states where the nominee rarely mentions Bush or Democratic challenger John F. Kerry.

For example, a frequently run TV ad in South Dakota, financed by the National Republican Senatorial Committee, shows Kerry and Sen. Edward M. Kennedy (D-Mass.) rebuking Bush, followed by 2003 footage of Daschle criticizing the diplomatic approach to the Iraq invasion. The narrator says Daschle is "leading the Democratic attack on President Bush."

In addition, Democrats see a new opportunity in Kentucky, where Sen. Jim Bunning (R) has come under scrutiny for what critics describe as odd behavior, including suggesting that his opponent, state Sen. Daniel Mongiardo (D), looks like one of Saddam Hussein's sons.

Dewar reported from Washington.

Senate Minority Leader Thomas A. Daschle (D-S.D.), left, speaks with Dorothy Olson of Sioux Falls, S.D., after a town meeting on Medicare reform. Republican John Thune, right, is trying to unseat the Democrat, who is holding a slight lead in polls in the thinly populated state.