As the presidential race continues to roil the Democratic Party, a consensus is growing among party deal-makers that superdelegates to the national convention should show their cards before the official gathering in August.

It is becoming increasingly obvious that Democratic lawmakers will play a key role in deciding the party’s nominee. All Democratic Members of Congress are superdelegates, the unpledged elected officials to the Democratic National Convention in Denver who collectively are likely to cast the deciding votes between their colleagues in the nomination hunt: Sens. Hillary Rodham Clinton (N.Y.) and Barack Obama (Ill.).

By a Roll Call tally as of Friday, 94 Democratic House Members and Senators have endorsed Clinton and 87 have thrown their weight behind Obama.

In the undecided column are 104 lawmakers, including several from the upcoming primary states of Pennsylvania, Indiana, North Carolina and Oregon. Altogether, Members account for 36 percent of the 794 total superdelegates.

“It’s a political calculus,” explained Tad Devine, a veteran strategist of Democratic presidential campaigns, referring to how superdelegates make up their minds.

“Some people are very much affected by the macro race — who’s winning the nomination for president. Other people are influenced by who would be the best candidate in their state,” Devine said. “There’s a third level, which is the kind of relationship people have” on a “human basis” with Obama and Clinton.

Devine believes there will be a “third wave” of delegate support that coalesces after the June 3 conclusion of the primary season in which the final bloc of superdelegates will move toward the candidate with the most momentum.

One key Senator — Bob Casey (D) of Pennsylvania — jumped off the fence on Friday, appearing with Obama in Pittsburgh to endorse the Illinois Democrat.

The endorsement may give Obama a boost among white, working-class voters who may be more conservative in their social leanings — Casey opposes abortion rights and gun control. Obama needs help in the April 22 Keystone State primary; Clinton has been leading him there by double digits in the polls.

“I believe in my heart that there is one person who’s uniquely qualified to lead us in that new direction, and that is Barack Obama,” Casey said Friday.

Freshman Rep. Jason Altmire (D-Pa.), who is undecided and has been heavily courted by both sides, said his office was being flooded with calls from voters claiming they won’t vote to re-elect him if he endorses the wrong candidate.

“I’m seeing in my district that the two sides are really starting to dislike each other,” Altmire said. “The two sides have generated such animosity towards each other that if this thing drags out for the next three months, it’s really going to be a bad situation.”

Twenty-two Democratic Senators remain undecided in the presidential race. But one prominent Obama backer — Sen. Patrick Leahy (D-Vt.) — suggested Friday that Clinton would be better off in the Senate. “There is no way that Sen. Clinton is going to win enough delegates to get the nomination,” Leahy said Friday on Vermont Public Radio.

“She ought to withdraw and she ought to be backing Sen. Obama. Now, obviously that’s a decision that only she can make. Frankly, I feel that she would have a tremendous career in the Senate.”

Leahy expressed concerns about the drawn-out Democratic primary fight.

Arizona Sen. John McCain, the presumptive GOP nominee, “is getting a free ride on it because Sen. Obama and Sen. Clinton have to fight with each other,” Leahy continued. “I think that her criticism is hurting [Obama] more than anything John McCain has said. I think that’s unfortunate.”

In a measure of worry about the prospects of the fight going to the convention floor, party leaders emerged last week to float various scenarios for resolving the contest earlier.

Democratic National Committee Chairman Howard Dean told CBS News on Friday that he favors the idea of superdelegates making up their mind before July 1, though that date was described by party operatives as not set in stone.

“Well, I think the superdelegates have already been weighing in. I think that there’s 800 of them and 450 of them have already said who they’re for,” Dean said.

“I’d like the other 350 to say who they’re [backing] at some point between now and the first of July so we don’t have to take this into the convention.”

Earlier in the week, Tennessee Gov. Phil Bredesen, who is neutral, floated the idea of a “superdelegate primary” in June in which elected officials would cast their vote before the August convention. Bredesen is worried that the protracted warring between Obama and Clinton will fatally damage the party’s chances of beating McCain.

But that idea was met with skepticism from Democratic aides on Capitol Hill, who questioned whether it is logistically possible.

Dean has not endorsed that idea, according to spokeswoman Stacie Paxton.

Some party insiders believe it will fall to Democratic leaders like Speaker Nancy Pelosi (Calif.) or Senate Majority Leader Harry Reid (Nev.) to broker a peace accord if neither candidate concedes defeat after the primaries.

Echoing other party leaders, Reid expressed confidence last week that the fight would end before August. But neither he nor his aides would elaborate.

“I think this has been a great campaign. The Democratic problem will be over before the convention, and I think it will all work out well for America,” Reid told The Associated Press.

Last week, Pelosi reiterated her long-held stance that the superdelegates should make up their minds based on the primary results.

“Speaker Pelosi is confident that superdelegates will choose between Sens. Clinton or Obama … before the convention in August,” spokesman Brendan Daly said. “The Speaker believes it would do great harm to the Democratic Party if superdelegates are perceived to overturn the will of the voters.”

Clinton’s allies may have angered the Speaker, however, with a missive to Pelosi last week asking her to change her public statements to acknowledge that superdelegates are free agents and can independently decide which candidate to support. The letter stated that the donors were party leaders and had also supported the Democratic Congressional Campaign Committee.

Torey Van Oot contributed to this report.