So what’s going on down at 555 Fourth St. NW, that fortress-like stronghold of U.S. Attorney Ronald C. Machen Jr.? District residents searching for signs of progress in Machen’s investigation of the city’s 2010 mayoral campaign might conclude: Not much.

Would that be an accurate assessment? Where you stand on that question depends on where you are sitting.

If you are occupying a cell in an Alabama federal penitentiary, as is former Ward 5 D.C. Council member Harry Thomas Jr., or if you are wearing an ankle bracelet and serving a home detention sentence, as is former council chairman Kwame Brown, you might be inclined to think that Machen and his crew have been a tad too busy.

But if you happen to be, say, Sulaimon Brown, you may be wondering if Machen is even showing up for work. Brown is the minor mayoral candidate who triggered the corruption probe in early 2011 when he told The Post that the campaign of mayoral challenger and council chairman Vincent C. Gray had paid him to stay in the race to harass then-Mayor Adrian M. Fenty.

Since then, three Gray campaign aides affiliated with the 2010 mayoral race — Howard Brooks, Thomas Gore and Jeanne Clarke Harris — have pleaded guilty to felonies. Otherwise, you might say all has been fairly quiet on the political corruption front.

“Not so,” Machen’s aides told me this week. The U.S. attorney has hardly been twiddling his thumbs, they said, since taking over the office in February 2010.

The aides produced statistics showing that since then, a total of 115 people have been found guilty or pleaded guilty in the District to federal corruption charges.

Forty-one of those people were convicted in 2010 — 11 federal employees, two local government employees and 28 private citizens. Some of those cases involved the corruption investigation into the D.C. taxicab industry. The two local government employees were a District police officer and a former investigator and tax auditor for Chief Financial Officer Natwar Gandhi’s Office of Tax and Revenue.

In 2011, the office recorded 39 convictions: 18 federal employees, five local government employees and 16 private persons.

So far in 2012, the aides note, the conviction tally is 35 — 13 federal employees, six local government employees and 16 private citizens.

These cases include Brown and Thomas as well as two former inspectors for the D.C. Department of the Environment, a former employee of the Office of Tax and Revenue, two former officials with the Army Corps of Engineers, and four former background investigators who screened federal employees.

Okay, I’ll give credit where it’s due. But what about that notable missed tackle?

In July 2011, the D.C. Board of Elections and Ethics referred allegations of financial wrongdoing in Kwame Brown’s 2008 campaign to the U.S. attorney. “It means we think there’s criminal activity here that needs to be looked into,” elections board chairman Togo West said at the time.

West was referring to an Office of Campaign Finance audit that, in the words of The Post’s Mike DeBonis, “found that Brown’s campaign failed to report contributions and expenditures totaling more than $270,000. The audit also found that the campaign passed $239,000 to a company owned by Brown’s brother, Che Brown, via a now-defunct consulting firm. A later complaint from the OCF alleged that Brown’s campaign failed to register a $60,000 bank account that Che Brown had control of.”

After nearly 16 months of investigation, Machen’s probe of the election board’s Brown referral ended with nary a peep.

Sure, Che Brown was charged on Wednesday and is expected to plead guilty to a single felony count of bank fraud. And Kwame Brown’s ankle bracelet is the result of his conviction on a similar count. But the charges against both brothers are unrelated to the allegations of financial wrongdoing in Kwame Brown’s 2008 campaign.

Machen’s supporters point to Kwame Brown’s resignation from the council, convicted-felon status, current home detention and public humiliation as proof of justice rendered.

These feds don’t know the District. Wrist-slapping and tongue-lashing are the cost of doing business here.

In our fair city, the powers of forgiveness and redemption and the capacity to selectively delete unpleasant memories know no bounds.

Feds: Check out Kwame Brown two years from now. Don’t expect him to be down and out.

As for the Gray campaign of 2010, with the exceptions of Brooks, Gore and Harris, things for the moment are pretty much where they were when Sulaimon Brown went public with his allegations.

Machen broke on the scene guns drawn, ready to take on the corruption challenge.

It brings to mind President Obama’s words to Republicans in September 2011: “Show us what you got. . . . The time for Washington games is over.” Some of those keeping an eye on the Gray administration are directing that same challenge to Machen now.