The question during the historic Watergate hearings in the 1970s was "What did he know, and when did he know it?" When the answers became known, President Richard Nixon had no choice but to resign.

The same question looms following Thursday's arrest of Assembly Speaker Sheldon Silver. "What did Gov. Andrew Cuomo know, and when did he know it?"

Here's what we know from statements by U.S. Attorney Preet Bharara, investigative reporting (primarily by The New York Times), and the Silver charges.

Frustrated by his inability to win passage of legislative ethics reform, Mr. Cuomo convened the Moreland Commission to investigate corruption in Albany, including among legislators. Since the legality of doing so was suspect, he appointed district attorneys who would have power to investigate legislators, as well as key staff members he expected to control the inquiry.

But the Moreland Commission—whether the staff or members, we don't know—acted much more independently than expected. One flash point was its decision to look into New York City real estate interests. In retrospect, that was crucial, given developer Leonard Litwin's prominent role in the charges against Mr. Silver.

After months of behind-the-scenes struggle over the investigations, Mr. Cuomo suddenly dissolved the commission as part of last year's budget deal in return for ethics reforms that even the governor admitted were inadequate. The U.S. attorney was angered by the move and grabbed the commission's files to make sure what it had found would not be buried.

A few weeks later, at a Crain's editorial board meeting, the governor blurted out his view that he was perfectly right to disband the panel. "The Moreland Commission was my commission," Mr. Cuomo explained. "It's my commission. My subpoena power, my Moreland Commission. I can appoint it; I can disband it. I appoint you; I can un-appoint you tomorrow.''

That also did not sit well with the U.S. attorney—or lots of other people, like New York Times reporters.

The cynical explanation has always been that Mr. Cuomo saw the commission as a tool to force Mr. Silver into a budget deal on the governor's terms.

The charges allege that Mr. Silver was increasingly desperate to derail the Moreland Commission because he knew his law-firm referral payments couldn't stand scrutiny. The allegation is based in part on statements by the governor's staff.

The bottom line is that the commission had developed information that helped lead to the arrest on corruption charges of the second-most-powerful official in the state.

Thus the question: What did the governor know, and when did he know it?

At a Daily News editorial board meeting Thursday, the governor again defended his decision. "If anything, it vindicates what happened," Mr. Cuomo said. The complaint suggests the U.S. attorney developed most of the information about Mr. Silver's outside income.

In the end, maybe it wasn't illegal for the governor to abolish the Moreland Commission, even if he knew it had developed damaging information about Mr. Silver. However, Mr. Cuomo's reputation and future in politics might never recover.