When you formally "separate" from your spouse, is your marriage legally over, or is there some sort of 'holding pattern'?

Some states a legal separation is required before a divorce. You can’t get a divorce without one.

A legal separations most important function is that from that moment forward any debts accrued belong to the individual partners and are no longer joint. Because divorce can take time to settle, sometimes years, so stopping potential joint debt is wise, obviously.

Huh. I had no idea separation was a legal thing, I thought it was just living apart while you go through the divorce.

The Gores are divorced.

The State of California had a court ruling just this month that separation occurs at the time one spouse moves out. A couple had divorced but lived in the house together to save money. One tried to avoid responsibility for debts; the Court said they had never separated for determination when finances were apart.

Wiki still shows Tipper Gore as separated, as does Al Gore’s.
Reports are that they still spend a fair amount of time together. Maybe they just wanted to be spared the media circus a divorce would have been. If one of them wants to remarry now, a divorce would be ho-hum.