Earlier this month, senior law enforcement sources leaked to the Associated Press the fact that the FBI has launched a nationwide investigation into whether ACORN is involved in a co-ordinated scheme to commit voter-fraud across the country.

In response to the AP report, several former DOJ voting-rights officials told TPMmuckraker that the decision to launch such an investigation so soon before an election -- not to mention the act of leaking it to the press -- is reminiscent of the politicization of DOJ that was exposed in the US Attorneys scandal.

But since then, we've seen few concrete facts about the probe. So it's worth taking a moment to lay out what we know, and what it might amount to.

Almost as soon as the news was reported, department sources tried to walk it back a bit, telling the New York Times that they were "wary of being pulled into a highly partisan controversy so close to Election Day," and stressing that the investigation would focus on separate state-based reports of ACORN submitting fraudulent voter-registration forms.

As we reported after the news broke, DOJ policy discourages law enforcement authorities from taking any action in the lead-up to an election which might "chill legitimate voting activities," as the department's own manual puts it. On Friday, some former department officials wrote a letter to Mukasey making exactly this point. (Though it's also worth remembering that under Alberto Gonzales, DOJ made changes to its manual that make it easer to bring voter-fraud cases closer to election day.)

The bureau may be sensitive to those concerns. ACORN itself says it still hasn't been formally contacted by the FBI in connection with a nationwide investigation, and we've seen little evidence that the bureau is proceeding with a heavy hand on the national level.

Still, in several states there's evidence of FBI involvement following complaints from local election officials about voter-registration fraud tied to ACORN.

In New Mexico, the Bernalillo County Clerk met with investigators from the FBI and the US Attorney's office, after passing on around 1500 suspicious forms submitted to her office -- in an area where ACORN is active.

In Missouri, the GOP-led Kansas City Elections Board said the FBI is looking at 600-800 suspicious forms after ACORN submitted 19,000 in the city.

And in Nevada, the FBI is part of a joint federal-state task force announced earlier this year to look into voter fraud, though a raid on a Las Vegas ACORN office conducted earlier this month was led by the office of Democratic Secretary of State Ross Miller.

Both the Obama campaign and House Judiciary chair John Conyers have suggested that the investigation is politically motivated.

That skepticism makes sense, especially given the Bush administration's well-documented history of pushing DOJ toward bogus, politically motivated voter-fraud prosecutions -- which we were reminded of Friday, when the White House asked the department to take action on a voter-suppression bid by the Ohio GOP, that had already been rejected by the U.S. Supreme Court. And the fact that the probe was launched just as national Republicans -- including, in a televised debate, John McCain -- were trying to turn ACORN into a national boogeyman tied to Obama adds to suspicions.

But so far, there's little evidence that, at ground level, the conduct of the investigation itself could be described as overly aggressive or as intended to influence the election. Though of course, one reason for the apparent softly-softly approach is that no evidence has yet emerged that ACORN has been involved in a nationwide voter-fraud scheme -- the supposed subject of the investigation.

But you can bet we'll be watching this closely from now to election day -- and beyond.