"You know, I was almost getting ticked off at the Democrats," said retail clerk Mavis Rullard as she carefully organized the seven flavors of beef jerky on sale at Cubby's, a tiny trading post on the vast khaki prairie that stretches out below the Badlands.

"They was in this store three or four times on Tuesday, saying, you know, 'Have you voted? Can we drive you there?' And I kept saying, you know, 'I'll vote when I get off work.' I mean, they went door to door all day, to get everybody over to the voting."

In the end, Rullard did vote -- Democratic, of course -- and thousands of her fellow Lakota Indians did as well, responding to an unprecedented drive by South Dakota Democrats to beef up voter turnout on the state's reservations.

Party leaders now say those new Democratic voters almost surely made the difference for incumbent Sen. Tim Johnson. He emerged from initial tallies Wednesday morning as the unofficial winner of one of the nation's tightest Senate races, with a 528-vote margin out of about 337,000 votes cast.

The margin is small enough that his Republican opponent, Rep. John Thune -- who was recruited for the Senate race by President Bush -- has a legal right to call for a recount. Thune says he will "wait and see" what to do, but he indicated he will not challenge the result absent some indication of fraud or error in the tallies.

State officials said today that there is no sign of wrongdoing involving the voting in heavily Indian counties here. Despite the noisy allegations of "fraud" and "vote-stealing" on the reservations that made a media splash a month ago, the balloting on Tuesday was evidently untarnished.

The state's attorney general, Mark Barnett, who had called in the FBI to help investigate possible voter fraud on the reservations in October, moved to shoot down any suggestion that Johnson's win may have been tainted. "I don't see any evidence that anybody stole an election from anybody else," said Barnett, a Republican.

Barnett said his office is pursuing two cases of possible forgery on registration and absentee ballot forms, but added: "I don't want the suggestion out there that there is widespread fraud when we don't have any evidence of that."

Renee Dross, elections commissioner of Fall River County, who oversees voting and ballot-counting on the Pine Ridge reservation, said in an interview that "we had a huge increase in the number of votes over there, but no problems to speak of. I think maybe too much was made last month of a few isolated cases."

Going into this fall's campaigns, both major parties knew that South Dakota's two congressional races -- for the at-large House seat, and Johnson's Senate seat -- would be close. With relatively few contested seats elsewhere, one of the nation's least-populated states suddenly became the focus of national media and interest-group attention.

So much money and manpower poured in that virtually every known voter was personally approached by one or both sides. With polls showing registered voters almost evenly divided, the Democrats went prospecting for a new source of votes -- and came up with a gusher on the state's Indian reservations.

Here on the Pine Ridge reservation, nearly all the Oglala Lakota Indians are Democrats -- but not many of them vote. Turnout has generally run at 30 percent or lower, county records show.

So this fall, the state Democratic Party launched a huge registration and turn-out drive. "They came right into the classroom and signed us up," said Ohitika Tasso, 18, of Wounded Knee, a senior at Pine Ridge High School. "And on Election Day, they sent a bus to the front door of the school and took a whole bunch of us over to" the polling place.

Tasso is certain that the new Indian registrants were reliable Democratic voters. "It's just sort of basic knowledge around here that the Democrats do more for us," he says. "The Republicans, they don't even put their signs up on the res." A month ago, it looked as if this unprecedented effort in Indian country might backfire on the Democrats. Two people being paid by the party to register Indian voters were charged with forging documents. The local and national media made much of the cases, suggesting that the fraud ran much wider. That put Democratic candidates on the defensive.

Indian activists and Democratic leaders, in turn, charged that the fraud allegations amounted to a Republican ploy. The state's top Democrat, Senate Majority Leader Thomas A. Daschle, wondered out loud "whether there isn't a political agenda at play here to intimidate people who are new to the political process."

If that was the agenda, it didn't work. On Tuesday, the Pine Ridge reservation's recorded turnout was 48 percent. That's well below the average for civic-minded South Dakota -- which had a 71 percent turnout overall on Tuesday -- but nearly double the usual rate for Pine Ridge.

Pine Ridge's Precinct 3, for example, reported 19 voters in the 1998 midterm election. This year, the number of votes cast at the same precinct exceeded 300.

The big turnout on the reservation wasn't enough to save the Democratic House nominee, newcomer Stephanie Herseth, who lost to the state's long-time governor, Republican William Janklow. Janklow garnered 53 percent of the vote. But the reservation vote made the difference in Johnson's razor-thin margin over Thune in the Senate race. County returns suggest that 90 percent of Pine Ridge voters backed Johnson.

Of course, it's not certain that Johnson's 528-vote margin will hold up through final county canvasses and a possible recount. The last time South Dakota had a congressional election recount, 24 years ago, the man who came in second in the initial tally ended up the winner, by a whopping 139 votes.

And thus began the political career of a then-unknown Democrat named Tom Daschle.