As the Democratic nomination marathon neared a potential finish line, key senators said the results of Tuesdays South Dakota and Montana primaries will have a domino effect on uncommitted superdelegates quite possibly clinching the nomination for Barack Obama.

We want this locked up sooner rather than later, said Sen. Tom Harkin (D-Iowa), who has remained undeclared. Lets have the nominee and lets move on. Thats the common thread among the uncommitted superdelegates. I will be ready after tomorrow night.

With only 31 total pledged delegates at stake in the two states, Obama cannot win enough in the final two primaries to reach the 2,118 necessary to clinch the nomination. But Sen. Claire McCaskill (D-Mo.), one of Obamas strongest Senate supporters, said that she had spoken to enough uncommitted superdelegates around the country Monday to determine that he will reach the threshold necessary to claim the Democratic nomination by the end of Tuesday evening.

I think tomorrow will be a very big day. Ive spoken to 10 uncommitteds, and theyve said yes, theyll be committing [to Obama], and theyll be committing sometime tomorrow.

The magic number has been shrinking so quickly, McCaskill said.

Eight superdelegates announced their choices Monday six for Obama and two for Sen. Hillary Clinton (D-N.Y.). In addition, House Majority Whip James Clyburn (D-S.C.) confirmed that he will endorse Obama on Tuesday.

A group of 15 uncommitted Senate superdelegates met on Capitol Hill Monday to discuss how to proceed on making their endorsements.

It was a dialogue about how people are feeling, said Sen. Ken Salazar (D-Colo.), who noted that no decisions were made at the meeting Monday. For me, its who I think can win this thing in November.

When asked who that was, he said: I could make the argument for either one of them.

Salazar said there will be another meeting of uncommitted superdelegates Wednesday.

Sen. Benjamin Cardin (D-Md.), agreed that superdelegates must make their decisions this week, but he said its not up to superdelegates to come out with a unified decision. Rather, Obama and Clinton will have to mend the fences and move the party ahead, Cardin said.

Im going to pick the person who has the most support and has the best chance of winning, Cardin said.

At Mondays meeting, Cardin said there was no lobbying on behalf of Obama or Clinton, and there was no push for a unified statement among the remaining superdelegates. But Cardin said he emerged from that meeting believing the superdelegates would rapidly begin making their decisions public in order to close out the nominating process.

Sherrod Brown, also uncommitted, said, I told both Barack and Hillary that Id make a decision by the end of the week.

At least one Senate superdelegate, Sen. Carl Levin (D-Mich.), said hes not committing because he wants to get his delegation seated with full votes. The Democratic National Committees Rules and Bylaws Committee agreed Saturday to seat Michigans full delegation, but each delegate including superdelegates will only receive a half vote.

Im sticking to it, he said.

Sen. Barbara Mikulski (D-Md.), a Clinton superdelegate, said Monday that her colleagues should remain patient for now.

I think if they decided to do anything today, it would be precipitous, she said. They should do it when the process of electing delegates is over.

As to Clinton superdelegates like herself: We are unwavering. We will go through tomorrow night and well see where Sen. Clinton is.