By Yang Qingchuan

Sen. Barrack Obama of Illinois and rival Sen. Hillary Clinton of New York are competing fiercely in the North Carolina and Indiana primaries Tuesday, the latest critical day in the Democratic presidential nomination race.

For front-runner Obama, the primaries present an opportunity to wipe out doubts about him being a "flawed" candidate in the general election.

It could also be an opportunity for Clinton to make the case that Democratic voter sentiment is swinging in her favor, and thereby cut into Obama's lead in pledged delegates and in the popular vote.

The results of Tuesday's primaries will be important for both candidates.

After all, the largest number of national convention delegates are at stake now than during the remaining primary season.

There are 72 convention delegates at stake in Indiana and 115 in North Carolina.

However, barring the most unexpected-- a blowout in either state, or twin victories by either Obama or Clinton -- the more likely outcome is a continued and inconclusive fight.

Three scenarios

There are basically three likely scenarios at the end of Tuesday's primaries.

First, Clinton wins Indiana and North Carolina. But analysts say this scenario will be most unlikely, based on pre-election polls.

Obama seems to hold a formidable advantage in North Carolina where African Americans account for a large chunk of Democratic voters while Clinton's best chance is to win Indiana with the support of white blue-collar workers.