Prospects improved that John McCain and Barack Obama would hold their first presidential debate on Friday as Congress made progress toward an agreement with the Bush administration on a $700 billion bailout of the financial industry.

McCain’s campaign has said the Republican wouldn’t participate in the debate unless there was a consensus. Obama still wants the face-off to go on, and the Democrat is slated to travel to the debate site in Mississippi on Friday.

“There’s no deal until there’s a deal,” McCain spokesman Brian Rogers said after Republicans and Democrats agreed in principle to terms of the bailout. He said the developments did not change McCain’s plans, though he added: “We’re optimistic but we want to get this thing done.”

Senior McCain adviser Mark Salter did not rule out attending the debate, saying: “We’ve got to see.”

The debate over the debate is the latest campaign twist as McCain and Obama try to navigate the uncharted politics of the financial meltdown and show leadership at a time of national angst. The two met with President Bush and bipartisan congressional leaders Thursday afternoon at the White House on the crisis. They sat three seats away from the president, McCain to his right, Obama to his left.

“With so much on the line, for America and the world, the debate that matters most right now is taking place in the United States Capitol — and I intend to join it,” McCain said while addressing former President Clinton’s Global Initiative in New York early Thursday.

Obama argued the debate should proceed because a president needs to be able to handle more than one issue at a time.

“The American people deserve to hear directly from myself and Sen. McCain about how we intend to lead our country,” he said. “The times are too serious to put our campaign on hold, or to ignore the full range of issues that the next president will face.”

In Oxford, Miss., debate organizers continued to prepare.

At a news conference, Mississippi Gov. Haley Barbour, a Republican, said he expected the presidential debate to go ahead, though he said he had no inside information. “This is going to be a great debate tomorrow night,” Barbour said.

Television networks, too, were moving forward. “We’re proceeding as if it’s on and will until someone tells us that it’s not,” ABC spokeswoman Cathie Levine said.

The two candidates spoke to the Clinton Global Initiative — McCain in person, Obama via satellite — before heading to Washington.

Presidential politics was running smack into the delicate negotiations over how to stop further weakening the sagging economy without putting an enormous new burden on taxpayers or rewarding corporations or their executives who share the blame for the woes.

On Capitol Hill, Democratic and Republican negotiators emerged from a closed-door meeting to report an agreement in principle they would present to the administration.

Rogers said McCain didn’t participate in that meeting, but was in talks with Republican leaders afterward. Conservative Republicans were among the holdouts, and there were indications they were waiting for McCain to make a move before they did.

An Obama campaign official said the Illinois senator called into the earlier meeting. His campaign said Obama learned of the tentative agreement upon landing in Washington; he had no immediate response.

As Thursday began, McCain again portrayed his announced halt to campaign events, fundraising and advertising — which he said would begin after the Clinton speech — as an example of putting the country ahead of politics. But in doing so he also hoped to get political credit for a decisive step on a national crisis as polls show him trailing Obama on the economy and slipping in the presidential race.

Despite McCain’s stated campaigning hiatus, Alaska Gov. Sarah Palin, paid a highly visible visit to memorials in lower Manhattan to those killed in the Sept. 11, 2001, terrorist attacks. However, the usual flood of McCain campaign and Republican National Committee e-mails to reporters attacking the other side slowed to a trickle. Still, McCain campaign aides appeared on news programs earlier in the day and it was unclear whether all of McCain’s TV ads were off the air.

Industry officials said Obama’s campaign was inquiring about buying airtime made available where McCain was absent. But McCain’s campaign also has indicated to TV stations that they may soon return to the airwaves.

Obama’s campaign derided McCain’s claim to have halted activity as a political stunt. Spokesman Bill Burton said in a statement: “John McCain hasn’t suspended his campaign, he only wants us to suspend disbelief.”

The Democrat also rolled out a new 60-second TV ad to run in “key targeted states” in which he cited economic policies endorsed by Bush and McCain as essentially to blame for the troubles.

“For eight years we’ve been told that the way to a stronger economy was to give huge tax breaks to corporations and the wealthiest. Cut oversight on Wall Street. And somehow all Americans would benefit,” Obama says in the ad. “Well now we know the truth. Instead of prosperity tricking down, the pain has trickled up. We need to change direction. Now.”