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The Thomases (Getty)

Supreme Court Justice Clarence Thomas' wife is getting him into trouble again.

Last October, Virginia Thomas left a bizarre voice mail message for Anita Hill, demanding that she apologize for the sexual harassment accusations Hill brought against her husband ... 19 years earlier. A month later, Mrs. Thomas drew negative attention for her post as head of Liberty Central, a Tea Party organization opposed to the "tyranny" of President Obama. Amid questions about whether the post was appropriate for the wife of a sitting Supreme Court justice, she resigned.

In her defense, though, the latest Virginia Thomas-related incident isn't exactly her fault.

On Thursday, several Democratic politicians called for a federal investigation into Clarence Thomas' failure to report his wife's income, for years, on financial-disclosure forms. Although Virginia Thomas earned nearly $700,000 from the Heritage Foundation between 2003 and 2007 alone, the Supreme Court justice checked a box labeled "none" under "spousal noninvestment income" on his annual financial-disclosure forms. In fact, he has routinely checked the wrong box for the 20 years he's served on the Supreme Court.

Twenty House Democrats, led by Rep. Louise Slaughter (D-N.Y.), sent a letter to the Judicial Conference of the United States asking for an investigation. In a statement attached to the letter, Slaughter wrote:

It is reasonable, in every sense of the word, to believe that a member of the highest court in the land should know how to properly disclose almost $700,000 worth of income. To not be able to do so is suspicious, and according to law, requires further investigation. To accept Justice Thomas's explanation without doing the required due diligence would be irresponsible.

Slaughter also noted that the Heritage Foundation, a conservative think tank, was a prominent opponent of the Affordable Care Act. Incidentally, the Supreme Court is expected to review the health care legislation in the near future, after the Justice Department's recent request for the Court to take it up.

The convenient timing of the Democratic push for an ethics investigation into Thomas -- just as the Affordable Care Act is brought before him -- may prompt grumbling from cynics who see it as a mere political play. But whatever the motive may be, repeatedly failing to disclose his wife's income for his entire tenure is a pretty drastic omission that he'll have a hard time defending.

What do you think -- an honest mistake or an ethical violation?

Cynthia Gordy is The Root's Washington reporter.