INDIANAPOLIS (AP) — Hillary Rodham Clinton eked out a win in Indiana as she struggled to halt her rival’s march into history.

Meanwhile, Barack Obama swept to a convincing victory in the North Carolina primary Tuesday night and declared he was closing in on the Democratic presidential nomination.

That made Indiana a virtual must-win Midwestern contest for the former first lady, who had hoped to counter Obama’s persistent delegate advantage with a strong run through the late primaries.

Returns from 99 percent of the Indiana precincts showed her with 51 percent to 49 percent for her rival, a margin of little more than 22,000 votes out of more than 1.2 million cast. The outcome wasn’t clear for more than six hours after the polls closed, the uncertainty stemming from slow counting in Lake County near Obama’s home city of Chicago.

“Tonight we stand less than 200 delegates away from securing the Democratic nomination for president of the United States,” Obama told a raucous rally in Raleigh, N.C. — and left no doubt he intended to claim the prize.

Clinton stepped before her own supporters not long afterward in Indianapolis. “Thanks to you, it’s full speed on to the White House,” she said, signaling her determination to fight on in a campaign already waged across more than 16 months and nearly all 50 states.

Returns from 99 percent of North Carolina precincts showed Obama winning 56 percent of the vote to 42 percent for Clinton, a triumph that mirrored his earlier wins in Southern states with large black populations.

Obama won at least 69 delegates and Clinton at least 63 in the two states combined, with 55 still to be awarded.

Voters in both states fell along racial lines long since established in a marathon race between the nation’s strongest-ever black presidential candidate and its most formidable female challenger for the White House.

The economy was the top issue by far in both states, according to interviews with voters as they left their polling places.

Two weeks after a decisive defeat in Pennsylvania, Obama sounded increasingly like he was looking forward to the fall campaign.

“This primary season may not be over, but when it is, we will have to remember who we are as Democrats ... because we all agree that at this defining moment in history — a moment when we’re facing two wars, an economy in turmoil, a planet in peril — we can’t afford to give John McCain the chance to serve out George Bush’s third term.”

Clinton was joined at her rally by her husband Bill, his face sunburned after hours spent campaigning in small-town North Carolina, and their daughter, Chelsea.

She stressed the issue that came to dominate the final days of the primaries in both states, her call for a summertime suspension of the federal gasoline tax. “I think it’s time to give Americans a break this summer,” she said.

She added that no matter who wins the epic race for the nomination, “I will work for the nominee of this party” in the fall campaign against the Republicans. To emphasize her determination, Clinton announced plans to campaign Thursday in West Virginia, South Dakota and Oregon, three of the remaining primary states.