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Another one bites the dust.

First, it was state Rep. Luis Arroyo, the Chicago legislator who was charged with bribery.

Now, it’s state Sen. Martin Sandoval, another Chicago legislator whose offices and home were recently the subject of a search warrant executed by the FBI?

It’s impossible to say which esteemed member of the Illinois General Assembly will be the next to submit a shotgun resignation as a consequence of alleged or suspected criminal behavior. But it’s a virtual certainty there will be a next one — it’s just a matter of time.

Arroyo announced his departure after Democratic House Speaker Michael Madigan made it clear that he was persona non grata in Springfield.It’s unclear who pushed Sandoval out the door — Senate President John Cullerton made it clear he doesn’t have the stomach to confront suspected corruption within his caucus. But someone — either inside or outside the General Assembly — must have because Sandoval’s well-deserved reputation as among the most marginal of the state’s many marginal public officials makes it clear he would never have done so as a matter of personal honor.

But last week, the onetime legislative power broker — chairman of the transportation committee and part of the Senate’s Democratic leadership team —reluctantly submitted his resignation after 16 years in the Senate.

“It is with a heavy heart, I, Martin A. Sandoval, do hereby resign the office of state senator” effective Jan. 1 at 12:01 p.m., Sandoval said in a letter to the secretary of the Illinois Senate.

In a statement that has zero credibility, Sandoval writes that “respect for my constituents and the Senate convinced me that this action is necessary in order to proceed without distraction to the important work that needs to be accomplished for working families throughout the state of Illinois in the future.”

Of course, if Sandoval really had any respect for either his constituents or the rest of the people of Illinois, he never would have engaged in the conduct that has federal investigators coming down on him like a ton of bricks.

The resignation announcement was Sandoval’s first public comment since the FBI agents ruined his upcoming holiday season by raiding his home and offices as well as the homes and offices of an array of Sandoval associates.

Sources have indicated that Sandoval is under investigation for taking payments in exchange for lucrative government contracts, probably construction.

News of the Sandoval raid sent Gov. J.B. Pritzker into a tizzy — he was openly expressing concern that his $45 billion public works program would be viewed with suspicion as a consequence.

That’s why the governor demanded that Sandoval be removed as chairman of the Senate Transportation Committee, where he used his influence to approve road building contracts.

The Sandoval probe is just one of multiple pending federal investigations that appear certain to sweep up public officials in Chicago, Cook County and the General Assembly.

One Chicago bigshot — Alderman Ed Burke — already has been charged with using his public office to gain favors and business from those who do business with the city.

That multi-year investigation, which featured a compromised former alderman who wore a wire to conduct thousands of conversations for federal agents, appears to be in its infancy.

Then there’s state Sen. Thomas Cullerton, who’s been charged in connection with a no-show Teamsters job. He was implicated by a top Teamster boss who’s cooperating with the feds.

Finally — at least it appears so — federal gumshoes are examining the broad lobbying apparatus employed by Exelon/Commonwealth Edison, and its ties to close political friends of Speaker Madigan.

Just as was the case in past public corruption investigations involving former governors Rod Blagojevich and George Ryan, the feds are reviewing a target-rich environment.

Ultimately, it may be that Arroyo and Sandoval represent the smaller of the fish to be caught in the feds’ expansive net. Whatever their status, they’re now gone and won’t be missed.