PIERRE, S.D. (AP) _ The voters of South Dakota look a lot like those who have favored Hillary Rodham Clinton in presidential primaries this year, but her rival, front-runner Barack Obama, has plenty of friends in high places in this rural state.

Not quite the stone faces atop Mount Rushmore. But most Democrats who've won statewide elections, past and present, in predominantly Republican South Dakota have endorsed Obama. These include former Sens. George McGovern, himself the Democratic presidential nominee in 1972, and Tom Daschle, the ex-Senate majority leader, and both Democrats now in Congress, Sen. Tim Johnson and Rep. Stephanie Herseth-Sandlin.

In addition, the Illinois senator has used his substantial fundraising edge over Clinton to field a larger ground organization in this sparsely populated state, which allocates only 15 national convention delegates in its June 3 primary but offers a larger psychological prize.

The last two primaries in the Democratic race, South Dakota and neighboring Montana, whose voters will distribute 16 delegates the same day, provide a final opportunity to display vote-getting power that might sway uncommitted superdelegates nationwide. These elected and party officials, whose convention votes are not bound by any primary, will provide the nominee's final margin of victory unless the final three primaries put Obama over the top.

"South Dakota and Montana get to be players in that, determining what the final message of the primaries will be," said Robert Burns, chairman of political science at South Dakota State University.

"It's important that Obama win both of them to convince the holdout superdelegates that he can win in predominantly white states," Burns said. "I think it's equally important to Clinton to show that in the last two primaries, she comes out a winner and is deserving of further consideration by superdelegates."

Obama is generally considered to be narrowly ahead of the former first lady here even though South Dakota's demographics appear to favor her.

Straddling the line between Midwest and West, South Dakota is overwhelmingly rural with corn and soybeans in the east and rolling cattle ranches and the Black Hills in the west. The state is 88 percent white, consistently ranks last in the nation in annual average wages and has the eighth-largest percentage of residents older than 65. Clinton has handily won states with electorates like this, most recently Kentucky and West Virginia.

No independent polls have been released in recent weeks, and both campaigns call the South Dakota race close.

"It's really, really hard to tell which way it's going to go," said Elizabeth Smith, a political science professor at the University of South Dakota.

Obama spent a day in South Dakota, talking about his rural policies in a dirt-floored building in Watertown and drawing a huge crowd in Sioux Falls. He planned another visit this weekend.

Clinton has been a more frequent visitor, holding rallies in cities large and small as she focused on farm policy, the economy and health care. With a week to go, Clinton's campaign announced that either she, her husband, the former president, or their daughter, Chelsea, would be in South Dakota every day until the primary.

Clinton was running a radio ad to blunt the perception that Obama is all but certain to get the Democratic nomination. "Tuesday we can show 'em. We can pick a president," the ad's narrator said.

Obama, meanwhile, was running ads emphasizing his message of change. Obama ads featuring Daschle described Obama as coming from a family of modest means with "the same values as most South Dakotans."

Both candidates highlighted their support of the farm bill and pledged support for ethanol and other fuels made from crops and for using wind to generate electrical power.