The political world will understandably be fixated today on the first day of oral arguments before the Supreme Court over the constitutionality of Obama’s health care law, his signature domestic achievement. But before getting to that, there’s another sleeper of a story that deserves some attention.

The AFL-CIO is set to call on a Republican member of the National Labor Relations Board to step down in response to a new report alleging ethics violations, perhaps the first time the union has taken this step. But there’s also an angle involving Mitt Romney: One of his advisers has also been implicated in the tale.

Last week, the NLRB’s Inspector General released a report finding that one of its members, Terence Flynn, had violated ethics rules by revealing confidential information about internal NLRB deliberations to former board members who used the info to benefit their private sector clients. This has been referred to the Justice Department, and if the charges are true, he may have badly compromised the integrity of the agency.

One of the recipients of this improperly divulged information, the report alleges, was Peter Schaumber, a former NLRB board member and labor relations consultant who is now a co-chair of Romney’s Labor Policy Advisory Group. In a statement to go out today, the AFL-CIO will call on Flynn to step down and for Romney to disassociate himself with Schaumber:

Even for an agency that has at times been highly politicized, these unethical practices are unprecedented and indefensible. NLRB member Flynn should resign immediately. The Department of Justice should quickly investigate and bring criminal charges if violations are found....

These findings also will be a test for candidate Romney. A key advisor has been found to have used his inside connections in a way that resulted in the violation of ethics rules. Allowing Schaumber to remain as an advisor will speak volumes about candidate Romney and the value he places on ethics in government officials. He should renounce these violations and dismiss Schaumber.

Romney has long been hostile to organized labor, regularly railing against “union bosses,” and the NLRB has long been the target of conservative ire. But this concerns a broader question: Whether Romney will keep on an adviser who has been implicated in allegations of a serious breach of governmental ethics.

* Supreme Court could still postpone decision: On to today’s main event: Today’s argument before the Supreme Court will be over whether an 1867 law that forbids suing over a tax before it has been collected means the case shouldn’t be argued until 2014 (when the mandate kicks in) at the earliest. On this front, like the argument over the mandate itself, a great deal turns on whether the court accepts the argument that it’s fundamentally a tax.

* The conservative case against the mandate: Jonathan Cohn has a useful primer on the primary “slippery slope” argument about liberty that opponents will be making to prove the unconstitutionality of Obamacare, and why the justices should reject it.

* Will unpopularity of health law impact Supreme Court decision? Robert Barns offers two key reasons reasons why it won’t: The Justices’ eagerness to prove they’re impartial and apolitical; and the tendency of public opion to eventually accept such major reforms as necessary solutions to pressing national problems.

* Public opinion still hasn’t turned around: The latest evidence: A new New York Times poll finding that the public disapproves of the law, 47-38, with a majority of independents also opposed.

And yet, the Dems’ best course is to continue owning the law anyway, since history has shown that arguments over major reforms can take decades to win.

* Legal insiders think law will be upheld: Former Supreme Court clerks and lawyers who have argued cases before the court think it’s unlikely that the law will be struck down. Tellingly, even people who have worked for the court’s conservative bloc agree.

* How Republicans intend to sell Ryan plan: Another big question for this week: With Republicans set to vote on Ryan’s new budget, can Republicans avoid a rerun of last year’s Medicare debacle? They are planning an aggressive effort to label the new version of Ryan’s Medicare plan “bipartisan” (based on Senator Ron Wyden’s support for it) and will stress that under the proposal, traditional Medicare remains an option.

But the plan isn’t meaningfully bipartisan and still tampers with Medicare’s traditional mission — which is why Dems think it will again drag the GOP down this year. Key question: Will Dems be able to use Ryancare to prevent Romney (who embraced the plan in the GOP primary) from achieving separation from the unpopular House GOP?

* Romney caught in an ideological trap in advance of general: Tom Edsall runs through the ways that untra-conservative GOP primary voters have forced Romney to pass ideological litmus tests that could render him toxic to independents.

Edsall thinks Romney will have a tough time repackaging himself in the general election. But much depends on whether the national media holds Romney accountable for the positions he’s taken during the primary.

* Wealthy voters heart Romney: Aaron Blake ferrets out a great detail from the exit polls on Romney’s loss to Santorum. They “showed him losing basically every demographic group in the state, with one notable exception: voters making more than $200,000 per year.”

* Three clarifying moments about today’s right wing: What do Ryan’s plan to radically redistribute wealth upwards, the shooting of Trayvon Martin, and the great Etch-A-Sketch moment all have in common? E.J. Dionne connects the dots.

What else?