NEW YORK (CNN) -- Sen. Barack Obama took a major step Tuesday toward securing the Democratic presidential nomination. He not only scored a convincing victory in North Carolina, but he also made Hillary Clinton's path to the nomination even more difficult by finishing closely behind her in Indiana.
Clinton vowed to soldier on, telling supporters at an Indiana rally that "it's full speed on to the White House."
Obama on Wednesday morning has a larger lead in pledged delegates as well as the overall popular vote. For Clinton, time for a rebound may be slipping away.
The finish line is 2,025 delegates. With North Carolina and Indiana in the rearview mirror, six contests and 217 pledged delegates remain.
In addition to wooing the dwindling pool of voters remaining in this nomination battle, Clinton and Obama are actively pursuing the roughly 280 uncommitted superdelegates, aides said.
These party insiders and elected officials -- who are granted special voting privileges at the national convention -- eventually will determine the next Democratic nominee.
Pressure is on Clinton to find a way somehow to halt what increasingly looks like an unstoppable Obama march to the nomination -- and keep the superdelegates from rushing to his corner before the primary season ends June 3. Watch a breakdown of Clinton's narrow win in Indiana »
Superdelegates will be closely monitoring Clinton's financial situation to assess her continued viability. One of her main challenges in the next month will be to raise enough money to compete with Obama in the final contests.
Clinton loaned her presidential race $6.4 million over the last month, her campaign said, an indication of her deteriorating financial position.
The senator from New York began the month of April with close to $32 million cash on hand, according to the most recent campaign reports filed with the Federal Election Commission. But only $9 million of that total could be spent during the primary season.
The report also showed Clinton owed more than $10 million, meaning her campaign was in the red even before she heavily stepped up television advertising ahead of Pennsylvania's April 22 primary.
Heading into Tuesday's contests, Clinton needed to win solidly in Indiana and pull closer than expected in North Carolina. Instead, the opposite happened.
In North Carolina, Obama cruised to an easy win by 14 percentage points, largely on the strength of overwhelming support of African-Americans and self-identified liberals and moderates. Geographically, Obama won every region of the state with the exception of the westernmost counties.
Clinton eked out one of the narrowest wins of this primary season in Indiana based on her continued solid support among older voters. Obama won voters age 17-64 by 6 percentage points, a margin that paled in comparison with Clinton's 38-point spread among voters 65 and older.
As in previous primaries, Obama performed better among college-educated voters, while Clinton captured the support of those without a college degree.
When it came to experience versus change -- central themes in this campaign -- Clinton once again dominated those voters more concerned with the former. Obama handily won voters who placed a higher priority on the need for change in Washington.
Looking ahead, there are some bright spots for Clinton. Next week, the campaign shifts to West Virginia, where the demographic and socioeconomic terrain ought to favor the former first lady.
On May 20, the candidates will battle it out in Kentucky and Oregon. Clinton is expected to do well in the former, while she will try to defy expectations in the latter. Her support among Hispanics also may bode well for her in the June 1 Puerto Rico primary.
Two days later, Clinton will battle it out with Obama in Montana and South Dakota -- the final two states in this marathon primary season. But unless she scores landside victories in the remaining contests, most pundits predict the delegates will be split about evenly between the two candidates.
Another hurdle for Clinton will be to find some way to convince Democratic leaders that the votes in Michigan and Florida should be counted.