Sen. Hillary Clinton's long night of soul-searching is about to begin. She has run out of plausible scenarios for wresting the Democratic presidential nomination from Sen. Barack Obama.

On Tuesday, Mrs. Clinton had counted on a big win in Indiana and a close race in North Carolina to buoy her claim to the nomination. The heart of her argument was simple: Despite his lead in pledged delegates and states won, Mr. Obama is a fundamentally flawed candidate with little appeal to most elements of the Democratic base.

What she got instead was a 2-point squeaker in the Midwest and a 14-point drubbing in the South -- not exactly the "game-changer" she was looking for.

If Mrs. Clinton had managed to win Tuesday the way she did two weeks ago in Pennsylvania, her argument may have resonated with on-the-fence superdelegates. But the wife of the former president couldn't close the deal.

The delegate math, which has not favored her since Super Tuesday, has become insurmountable. Even with a month of rocky press on Mr. Obama that included the re-emergence of Rev. Jeremiah Wright as a campaign issue, Mrs. Clinton was unable to convince voters to abandon him in the numbers she needed.

Still, she has not conceded the race. It is her right to soldier on, but it is an act of futility that may harm the party's chances in November. Though she will probably win the primaries in West Virginia and Kentucky, she will not be able to build enough momentum to claim the party mantle.

In her speech Tuesday night, she sounded some conciliatory notes to her opponent, including a repeated pledge to work on behalf of the Democratic nominee. Mr. Obama should seize the opportunity to reach out to her campaign. He should work with Mrs. Clinton on a solution for Michigan's and Florida's delegations so that the party is truly united at the convention; he should also offer help to retire her campaign debt.

With Indiana and North Carolina in the rearview mirror, the end game for the Democratic campaign becomes increasingly clear. The only way for the party to avoid more bruising before the fall showdown with John McCain is for superdelegates to end their silence and declare for the candidate with the numbers on his side.