WASHINGTON (AP) -- The entire top echelon of Newt Gingrich's presidential campaign resigned on Thursday, a stunning mass exodus that left his bid for the Republican nomination in tatters. But the former House speaker vowed defiantly to remain a candidate.

"I am committed to running the substantive, solutions-oriented campaign I set out to run earlier this spring," the Gingrich said in a posting to his Facebook page shortly after the 16 aides resigned. "The campaign begins anew Sunday in Los Angeles."

Rick Tyler, Gingrich's spokesman, said that he, campaign manager Rob Johnson and senior strategists had all quit, along with aides in the early primary and caucus states of Iowa, New Hampshire and South Carolina.

Other officials said Gingrich was informed that his entire high command was quitting in a meeting at his headquarters in Washington. They cited differences over the direction of the campaign.

"We had a different vision for victory," Tyler told The Associated Press. "And since we couldn't resolve that difference, I didn't feel I could be useful in serving him."

He said Gingrich was not allowing enough time to campaign in key states.

Scott Rials, a longtime aide who joined the departure, said, "I think the world of him, but at the end of the day we just could not see a clear path to win, and there was a question of commitment."

The upheaval in the campaign was likely to lead to a shake-up in the race for the party's presidential nomination, as well, as rivals reach out for disaffected staff, and possibly for donors who have been aligned with the former Georgia congressman.

Gingrich has long been viewed, by even his closest allies, as a fountain of policy ideas but a man who is unable to avoid speaking in ways that spark unwelcome controversy.

Even before the sudden departures of his top aides, Gingrich's campaign was off to a notably rocky start. Within days of formally announcing he would run, he was assailed by conservatives for criticizing a plan to remake Medicare that Republicans pushed through the House.

He telephoned the author of the plan, Rep. Paul Ryan of Wisconsin, to apologize but did not back off his objections.

Within days, he had dropped from sight, embarking on a cruise to the Greek Isles with his wife, Callista, while rivals for the Republican nomination kept up their campaign appearances.

He returned to the United States this week to confront a rebellion that had been brewing for some time among the senior echelon of his campaign.

Two aides said Gingrich had refused a request to show a copy of his personal schedule. The aides, speaking only on condition of anonymity, also cited his willingness to give his wife a large role in campaign decisions as a reason for the departures.

While Gingrich told his now-departed aides he would remain in the race, he faces formidable obstacles in assembling a new team in time to compete in a campaign that's well under way. He has the allegiance of several former aides who served him when he was in Congress, but most if not all of them have moved into other fields.

Most immediately, he is scheduled to participate in a debate next Monday in New Hampshire.

Johnson and another key aide, strategist David Carney, joined Gingrich's campaign after working as senior political staff members for Texas Gov. Rick Perry.

Perry ruled out running for the White House earlier in the year, but more recently has said he might reconsider. It was not known whether his former aides were interested in returning to him.

"Nothing has changed," the governor's spokesman, Mark Miner, said in an interview on Thursday. "The governor is focused on the legislative session."

Gingrich, 67, last served in public office more than a decade ago. He resigned as speaker of the House after two terms following an unexpectedly close mid-term election in 1998 in which Republicans gained far fewer seats than he had predicted.

In the years since, he has established a virtual one-man think tank, publishing books and speaking publicly.

Gingrich announced his presidential exploratory committee in May and is not required to report the results of his campaign fundraising until mid-July.

He has raised more than $52 million for American Solutions for Winning the Future, his nonprofit policy group that can legally accept unlimited donations.

But presidential campaigns are subject to much stricter rules — a candidate can accept a maximum contribution of $2,500 per person for the primary campaign and $2,500 per person for the general election.

In addition to Tyler, Johnson and Rials, aides who quit include senior adviser Sam Dawson, South Carolina director Katon Dawson, and New Hampshire director Dave Carney. The entire full-time staff in Iowa, six aides, also quit.

One of them, political director Will Rogers, left last week out of dissatisfaction with the direction of the campaign.

He said that as of May 31, the day he announced he was quitting, the candidate had not scheduled any campaign days in the state. The Iowa caucuses traditionally begin the delegate selection process, and assembling a network of supporters is an arduous process that usually requires a candidate's frequent presence.