West Virginia is 95 percent white, has the highest percentage in the nation of people without a college education, and the second-highest percentage of older Americans, after Florida.
Adding to her electability argument, Clinton repeatedly reminded voters over the last week that no Democrat has won the White House since 1916 without winning West Virginia, a state that voted for former President Clinton in 1992 and 1996 but voted for President Bush in 2000 and 2004.
The Clintons made 30 campaign stops in West Virginia, while Obama made three, and the many appearances the former president made may have paid off. A large majority of Clinton voters said Bill Clinton's campaigning was important to their vote, preliminary exit poll results suggest.
Despite her victory today, Clinton continues to lag behind Obama in delegates, momentum, and money.
Her campaign debt is estimated to exceed $20 million and could go deeper as she campaigns through the final primaries June 3.
Though the last Democratic contest is not until June 3, the Illinois senator has increasingly begun to focus his campaign on the general election.
This week he announced plans to visit important swing states Michigan and Florida -- which were stripped of their delegates to the party's convention this August in Denver after they broke party rules by moving their primaries ahead on the calendar.
While Clinton is facing increased pressure to drop out of the race, her senior adviser Terry McAuliffe told ABC News he is "100 percent" certain she will stay in the race until the last primaries in Montana and South Dakota on June 3.
But Obama said this week the nomination fight may be over on May 20, if his expected win in Oregon that day gives him a majority of pledged delegates.
Despite the bitter campaign and rumors of animosity between the candidates, the rivals were cordial when they were both on the Senate floor this morning on Capitol Hill.
Obama walked over to Clinton to shake her hand and pat her on the arm. Later, Clinton traveled to Charleston, W.Va., where she toured a farmer's market and shook hands with voters.
Despite Obama's insurmountable delegate lead, Clinton's continued presence in the race doesn't bother a majority of Democrats.
While most Democrats favor Obama for the nomination, 64 percent of likely Democratic voters believe she should stay on and fight, according to an ABC News/Washington Post poll released Monday.
"As long as she's not dividing the party deeply by going after Sen. Obama and questioning his capacity to be president, attacking him on issues, running negative ads like the '3 a.m.' ad, then I think she's fine and not damaging herself within the Democratic Party and certainly not damaging herself with voters," Devine said.
By staying in the race and continuing to win states, Devine argued, Clinton may enhance her image and close the gap in the popular vote.
"This process has been good for her, even though she is ultimately going to lose it," he said.
"That identity of fighting for people and the perception that she doesn't give up will serve her well in politics, particularly if there's some tough fights ahead like passing national health insurance, which she may take a leadership role on," Devine said.