Hillary Clinton is working overtime to try and pull out a win for the Democratic presidential nomination, campaigning in South Dakota on Thursday and arguing that she's the best candidate to help rural economies.

Clinton told FOX News on Wednesday she's taking her underdog fight "a step at a time," and that includes working to keep her campaign afloat through the end of the primary calendar, June 3.

The New York senator hosted 50 members of her national finance team at her Washington, D.C, home Wednesday and was preparing to meet with more superdelegates in her quest to convince them she's got the support to carry the party to victory in November.

Barack Obama dealt a heavy blow to Clinton when he unveiled the much-sought endorsement of former presidential candidate John Edwards. But the Clinton campaign argued that didn't change the fact she won the West Virginia primary by 41 percentage points the night before.

"I want to be crystal clear ... Hillary Clinton is going to one place. She is going to Denver as the nominee of the Democratic Party," campaign chairman Terry McAuliffe said Wednesday. "People are going to endorse, they are going to come out, but I think more important than anyone endorsing is what happened last night in West Virginia."

McAuliffe said earlier that the campaign had pulled in a seven-figure fundraising haul online Tuesday night. That would help, since Clinton faces personal campaign debt of more than $20 million and more than likely will end the primary season significantly in the red.

Though she's down by nearly 170 delegates with only five contests left, Clinton argued the Democratic race must run through June 3, and possibly beyond.

"Nobody has the numbers yet," she told FOX News on Wednesday. "So are we in the last two minutes of a game that you don't think one or the other can win? You go to the buzzer, maybe it goes into overtime. We don't know. ... And until it's over, it's not over."

Clinton was not specific on what she meant by "overtime."

"We're going to -- let's take it a step at a time," she said when asked whether she was talking about taking the race to the convention floor in August.

But Clinton has effectively moved the goalposts, which could explain why she's pondering a race that lasts beyond June 3. Instead of the 2,026 total delegates Obama is striving for to clinch the nomination, Clinton insists "the number of delegates you have to get is 2,210."

That includes Florida and Michigan, states that were discounted because they held early primaries in violation of party rules. Clinton won those states and still is holding out hope for a rules panel of the Democratic National Committee to meet May 31 and discuss the ongoing dispute over Michigan's and Florida's delegates.

Clinton won big among white and working-class voters in West Virginia, but on Wednesday she backed away from comments she made a week ago, when she talked up her ability to win those voters in an interview with USA Today.

"I regret deeply that, you know, rather than my referencing what was I thought an objective source talking about how this campaign has unfolded, anybody would attribute that to me," she said, explaining that she was simply quoting a wire service story when she noted the demographic trends.

Clinton has won a larger percentage of white voters than Obama in 27 states, while Obama has won those voters in seven states.

The New York senator continued to talk up her electability come November.

"Democrats have lost in 2000 and 2004 because we didn't win in rural areas," she said, highlighting her ability to pick up support outside urban centers. "And I think that is a really strong indicator, because I believe that a Democrat will win in the cities, whoever our Democrat is."

Meanwhile, Obama continued to rack up endorsements Wednesday despite his double-digit loss the night before. Edwards was the big haul for the Illinois senator.

Both candidates courted the former North Carolina senator after he dropped out of the race in late January. Though Obama lost West Virginia in a landslide, he won North Carolina last week by double digits.

Click here to watch Clinton's interview with FOX News.

Click here to read the full transcript of the Clinton interview with FOX News.

FOX News' Major Garrett and The Associated Press contributed to this report.