Democratic presidential hopeful, Sen. Barack Obama D-Ill., meets with workers at the Rite-Aid Distribution Center during a campaign stop in Waterford, Mich., Monday, 02 June 2008

The marathon-like U.S. Democratic party presidential primary election season comes to an end Tuesday as voters cast ballots in the last two state contests.

Senator Barack Obama is likely to win the long and hard-fought battle with Senator Hillary Clinton for their party's nomination.  

But, with relatively few delegates (31) at stake today in the states of South Dakota and Montana, Obama will not be able to secure victory based on the primary election results.

That means the final outcome will be decided by so-called superdelegates, officials and elected office holders who are free to vote for either candidate at the party's nominating convention in August.

Party officials say they think enough superdelegates will announce their support for Obama after the polls close to give him the nomination.

Obama is planning to formally start his general election campaign against presumptive Republican presidential nominee Senator John McCain with a rally tonight in the central state of Minnesota.

Obama won the support of a key superdelegate today. South Carolina Congressman James Clyburn, the third-highest ranking Democrat in the U.S. House of Representatives announced he favored Obama.

Meanwhile, the Clinton campaign gave signs that it may have entered its final days.

Former President Bill Clinton told a crowd of supporters in South Dakota Monday that it might be the last day he would be involved in a campaign like this one.  He said it has been an honor to campaign for his wife.

Some Clinton field staffers were told Monday their services would no longer be needed.

At a campaign stop in Michigan, Obama praised Clinton.  He said she has run an outstanding race.  He also said he looks forward to meeting Clinton at a time and place of her choosing, and he promised to do all he can to unify the party before the general election.

Some information for this report was provided by AFP, AP and Reuters.