GWEN IFILL: Neither Hillary Clinton nor Barack Obama had public events this final primary day. Voters did head to the polls in South Dakota and Montana, but most attention was on Capitol Hill, where uncommitted super-delegates control the balance of power.
NewsHour congressional correspondent Kwame Holman reports.
KWAME HOLMAN: South Carolina's James Clyburn was helping lead the effort today on Capitol Hill to recruit unpledged super-delegates to Barack Obama's side.
REP. JAMES CLYBURN (D), South Carolina: I have been trying to get enough super-delegates to commit to Senator Obama today so that, when he has a big rally in Minnesota tonight, he will be able to give credit to the voters of South Dakota and Montana the threshold reach rather than to those of us here inside the Beltway.
I just thought it would be a much better narrative for that to happen than for him to come to us on Wednesday and need the so-called super-delegates in order to get to 2,118. Get there with the voters.
KWAME HOLMAN: That may not happen as Clyburn has planned, but the Associated Press still reported today that Obama had effectively clinched the nomination.
That was based on public declarations of support, private commitments, and the 11 pledged delegates Obama would receive if he wins at least 30 percent of the vote in today's primaries in Montana and South Dakota.
This afternoon, Senate Majority Leader Harry Reid refused to declare the race over and he urged his colleagues to hold off on making their support known.
SEN. HARRY REID (D-NV), Senate Majority Leader: I believe that we should wait until after the primaries are finished. If, in fact, it's as you've said -- and I don't accept anything at this stage -- Senator Clinton needs to be left alone. And let's get through the primary process and let this week work its course.
KWAME HOLMAN: Iowa's Tom Harkin, one of the Democrats' remaining undeclared senators, appeared ready to respect Reid's request.
SEN. TOM HARKIN (D), Iowa: I said a long time ago I was not going to do anything until after the primaries were all over with. I believe in playing by the rules.
I felt that every state ought to have its right to cast its vote. Plus, the fact, with my own populist background, I don't much believe in super-delegates anyway, and I hope we do away with the whole thing. It smacks of elitism, and I don't like that.
But the fact is we are super-delegates, so we'll have to cast a vote. And so, I'll be -- as I said, I wouldn't do anything until after the primaries, so tomorrow, on Wednesday, I'll be making my decision at that point in time.
KWAME HOLMAN: But Clyburn said now was the time to move on from the primary and bring the party together.
REP. JAMES CLYBURN: Unity can come in many different forms. And so I think that if they will let the American people, that we are on the same page, and that it's up to Senator Obama to decide who to invite on the ticket with him, that he will go through a process over the next few days of vetting his choices, in order to determine who is in the best interest, and the two of them will rally around that ticket, irrespective of how it is composed, I think that's what they've got to do.KWAME HOLMAN: Obama has said he would be willing to meet with Senator Clinton once the primary process has ended at a time and place of her choosing.