Correction: An earlier version of this column about the federal investigation into the District's 2010 mayoral campaign mistakenly switched names in one reference. It was Howard Brooks, not Sulaimon Brown, who pleaded guilty to making false statements to authorities. This version has been corrected.

The D.C. corruption investigation led by U.S. Attorney Ronald C. Machen Jr. has entered a new phase, which could be described as “We ask, you tell.”

How different today’s climate is from spring 2011.

That’s when mayoral candidate Sulaimon Brown told The Post he had been paid during the 2010 Democratic mayoral primary by members of Vincent Gray’s campaign — chairwoman Lorraine Green and consultant Howard Brooks — to continue a verbal assault on incumbent Mayor Adrian M. Fenty in exchange for money and the promise of a city job.

The Gray campaign’s response at the time was dismissive.

Sulaimon Brown? He’s that “annoying guy who wouldn’t go away,” Gray’s senior strategist Mo Elleithee told The Post.

“If anything happened, and I don’t believe it happened . . . I would be shocked to find out anything did happen,” Gray campaign manager Adam Rubinson chimed in.

Brooks told The Post that he never made payments to Brown and explained the records of his phone calls with Brown by saying he had spoken to several rival candidates. Brooks declined further comment.

Green, meanwhile, got her back up.

She said in a statement that Brown’s allegation was a “smear campaign,” adding she had “retained an attorney to look into initiating legal action against Mr. Brown for the libelous, scandalous statements he is making to the news media and others against me.”

(Where’s the lawsuit?… Anyone?… Anyone?)

“Was there a quid pro quo here?” Gray asked The Post last year. “Did we ask him to do something on behalf of my candidacy, and did we give him something? The answer is unequivocally no,” Gray declared.

That was then.

Samuel Johnson’s 18th-century observation that “The prospect of a hanging concentrates the mind wonderfully” applies in this case.

Somewhere along the way, a gallows image may have entered the imagination of some Gray campaign operatives.

In May, Brooks told a U.S. district judge that he had been “instructed” to pay Brown secretly to stay in the mayoral race. Brooks confessed to giving Brown money orders worth $2,810, and he pleaded guilty to lying to federal authorities.

That confession ushered in the investigation’s “We ask, you tell” phase.

As part of his guilty plea, Brooks agreed to cooperate with the feds, which he has apparently done to a fare-thee-well.

The hidden recording device he wore during conversations with Thomas W. Gore, assistant treasurer of the Gray campaign, helped the feds to nail Gore.

Gore admitted in federal court to obstructing justice by destroying a spiral notebook containing a record of payments to Brown as well as other campaign finance misdemeanors.

Brooks’s cooperation was so exemplary that federal prosecutors filed papers in court this week recommending that he be sentenced to probation, not prison, because of his “substantial assistance.”

Message from Machen: Do a Howard Brooks, and you, too, might be given a “get out of jail free” card.

Prosecutors won’t say what Brooks said to them to make things right. But their glowing reference turns the mind to Sulaimon Brown, whom I incorrectly characterized in a recent interview as “wacky.” Brown is anything but that.

Which gets us to the charge Brown leveled during a June 2011 D.C. Council hearing — repeated to me during a phone conversation this week.

Brown told me that, in August 2010, during a gathering at the Eatonville restaurant on 14th Street NW (I recommend the gumbo), he stepped outside with Gray and Brooks. Brown said Gray thanked him for what he had been doing and added, “Howard has something for you.” Brown told me that Brooks then gave him some money.

Brown said Brooks could confirm this account to prosecutors.

What the prosecution has gotten from Brooks is under court seal.

I asked Brooks’s attorney, Glenn Ivey, about the Eatonville incident, but Ivey declined to comment.

But the momentum is clearly moving the U.S. attorney’s way.

To sum up, the “We ask, you tell” phase:

The prosecution has postponed sentencing of Gore and former council chairman Kwame Brown, who pleaded guilty in June to bank fraud. Public relations consultant Jeanne Clarke Harris admitted in court in July that she participated in an illegal scheme to disburse and conceal campaign funds in Gray’s campaign.

Because of their agreements with prosecutors to cooperate, Brooks, Gore, Kwame Brown and Harris have the makings of a chorus. They may be singing their hearts out, bringing sweet music to the prosecution’s ears and heartburn to a few fellow Washingtonians.

We live in hope.