Ever since Washington’s Occupy protesters pitched their tents in two high-profile spaces downtown, observers have been asking: Why two?

The answer wasn’t exactly clear. One camp, in Freedom Plaza, was founded by veteran antiwar activists; the other, in McPherson Square, by recent college graduates. While both groups advocated similar goals of economic justice, they fiercely prized their independence and some days barely got along.

Until now.

Facing an uncertain future, the two Occupy camps agreed in principle this week to join forces, with three dozen or so Occupiers probably packing up at Freedom Plaza and moving their vigil tents to McPherson in the next week or 10 days. The deal was cemented Friday evening, when activists at Freedom Plaza voted unanimously to approve the move. The group plans to keep an information tent at the plaza, however.

“The two occupations in Washington, D.C., are uniting in McPherson Square,” said Lacy MacAuley, 33, an Occupy protester. “We’ve been getting closer and closer and doing joint [protest] actions. So this is something that’s been in the air for a while.”

Carol B. Johnson, spokeswoman for the National Mall and Memorial Parks, said that in recent days the Occupiers at the federally owned Freedom Plaza had been negotiating for a new protest permit with the National Park Service. Their permit is set to expire April 29.

But when Park Service officials told them that they would have to vacate the plaza throughout the spring and summer to make way for other groups that had reserved it, they began to think about leaving. Occupiers in Freedom Plaza said they felt good about the plan to unify.

“It’s going to be fantastic,” said Barry Knight, 44. “Initially, there were differences in terms of age. McPherson started out with a much younger crowd. But I don’t understand how that age difference would be a negative if we merged. Diversity is a strength; division is a weakness.”

The two groups had moved into the federal parkland at different times in October in solidarity with the Occupy Wall Street movement but had long operated separately, each holding its own marches and creating separate governing structures.

The overnight campers remained in both spots for four months until U.S. Park Police evicted them in February, clearing the parks of bedding and debris while leaving a handful of tents behind. The Occupiers can maintain symbolic vigil tents in the public spaces, but are not allowed to sleep in them.

Park Service officials are grappling with the prospect that they could face bigger crowds in the park just as its spring refurbishment is underway, Johnson said.

On Thursday, Park Service employees began turning over the flower beds in McPherson Square and preparing to reseed some $8,000 worth of sod that was ruined during the long protest.