It was a smart move: About one-third of the party's 260-plus undeclared superdelegates are members of Congress, and they were a captive - and starstruck - audience yesterday, gathered in the Capitol for a series of votes.

"You go where the votes are," said Rep. Robert A. Brady, the Philadelphia Democratic chairman, who sparked the mob scene by suggesting that Obama pop over for a visit.

Entering the chamber a little before 11 a.m., Obama made a beeline for "Pennsylvania Corner," the spot in the back of the House where Rep. John P. Murtha, a Johnstown Democrat and supporter of Sen. Hillary Rodham Clinton, hangs out along with Brady and other members of the state's delegation.

Obama thanked Brady for inviting him. "He said, 'See that, Bob, I listen to you from time to time,' " recalled Brady, an undeclared superdelegate.

Brady was driving south on the Baltimore-Washington Parkway about 9:30 a.m., heading for work, when Obama called to check in.

"He was politicking me," Brady said.

As the conversation was wrapping up, Brady asked where he was. Obama said he was in the Senate.

"I said, 'Come on over,' " Brady said. "We're superdelegates, he should be over here."

Obama was meeting privately with members of the Blue Dogs, a caucus of moderate and conservative Democrats - many of them undeclared in the presidential race - and followed them to the House floor when they were called for a vote.

Although his lead in pledged delegates is insurmountable, Obama cannot win the nomination without superdelegates, the Democratic elected officials and party insiders who will have seats at the national convention in Denver in August and are not bound by the outcome of any state's primary or caucus. (For that matter, Clinton cannot overtake Obama without a stampede of superdelegates.)

Obama stayed in the House about 45 minutes, chatting with his declared backers, undecided lawmakers and Clinton supporters, and even some Republicans. He curtsied before Rep. John M. Spratt Jr. (D., S.C.), chairman of the Budget Committee.

Obama also was seen joshing with Murtha and Brady, as well as their uncommitted fellow Pennsylvanians, Reps. Jason Altmire, Michael F. Doyle and Paul E. Kanjorski.

Brady said he would remain officially neutral for now.

"I'm doing things to try to help bring this thing to a close, so it's best for me to stay where I'm at," Brady said, so both sides can see him as an honest broker. "We've got to do something."

He said he suggested to Clinton advisers that she, too, visit the House floor. She was campaigning in West Virginia and South Dakota yesterday.

Brady said both Obama and Clinton call him occasionally on their rounds of superdelegate stroking. He declined to describe his conversation with Obama yesterday, though he said it included "strategy, what he needs to do."

At the end of the day, Altmire, Doyle and Kanjorski also remained on the fence - though Altmire, a freshman from the Pittsburgh region, has indicated he is leaning toward Obama.

Two House-member superdelegates, Reps. Brad Miller of North Carolina and Rick Larsen of Washington state, did endorse Obama yesterday, though neither cited his triumphant tour of the chamber in doing so.

Obama also drew the endorsement of former House Democratic Whip David E. Bonior of Michigan, who managed John Edwards' 2008 presidential campaign.

"Our goal is going to be to try to bring the party together as soon as possible," Obama said, walking through the Capitol Rotunda after his visit to the House, surrounded by reporters and photographers. "But we still have contests remaining, and so in no way am I taking this for granted. We're going to have to keep on working."