THE ACCELERATING investigation into the 2010 election campaign of D.C. Mayor Vincent C. Gray has produced titillating revelations of bogus money orders, shredded records, a hidden wire and now, it appears, bald-faced lies to the FBI. But at the heart of the federal investigation is something precious and important: the integrity of the electoral process. What happened in 2010, as U.S. Attorney Ronald C. Machen Jr. made clear in a pull-no-punches statement, is that “the voters of the District of Columbia were deceived.”

The election of Mr. Gray (D), who campaigned against former Mayor Adrian M. Fenty (D) on a theme of restoring integrity to government, was aided by secret payments, fraudulent filings, stealth deals and dirty tricks. Those responsible for these underhanded tactics — and Mr. Gray has not been charged — are rightly being held to account as federal prosecutors proceed with an investigation entering its second year. Sadly, though, there is no way to undo whatever influence their misdeeds had on the electoral process.

Mr. Machen, whose office brought criminal charges Wednesday against a second member of Mr. Gray’s campaign team, decried what he saw as “pretty shocking” and a “flagrant” abuse of the system. “We take seriously — very seriously,” he told us, “the imperative that people play by the rules, that elections be fair and transparent. When you cross the line, you tamper with our very system of government.”

That’s exactly what happened when operatives for Mr. Gray secretly financed the candidacy of minor mayoral hopeful Sulaimon Brown so that he could continue the fierce attacks on Mr. Fenty that helped undermine the Fenty campaign. It is impossible to say whether the dirty tricks changed the outcome of the primary. Mr. Fenty faced plenty of problems of his own making. But the Gray campaign would not have gone to such lengths unless its strategists believed the scheme would have an effect.

Federal prosecutors are reported to be examining more than Mr. Brown’s claims that he was paid off with campaign money and the promise of a city job. They also may be looking into allegations of a “shadow campaign” that operated outside of campaign finance rules.

Documents in the government’s case against campaign official Thomas W. Gore, who pleaded guilty this week for his role in funneling and then trying to hide funds to Mr. Brown, contains a reference to “excessive or unattributed cash contributions.” Howard Brooks, the campaign consultant named in a criminal information filed Wednesday that is a likely prelude to his guilty plea, is believed to be cooperating with federal prosecutors, as is Mr. Gore.

Did Mr. Gray know what was going on? If not, why not? The mayor, who previously has denied wrongdoing, has refused to comment on the charges involving Mr. Gore and Mr. Brooks. That’s understandable but not sustainable. Surely the public is owed an explanation, and an apology, for the events that now taint the 2010 election.