In her letter to President Obama about Ms. White, Ms. Warren wrote that by not developing a political spending disclosure rule Ms. White was “ignoring the S.E.C.’s core mission of investor protection.” Actually, dredging up the details of political spending has nothing to do with protecting investors, though it might fall into the category of “things corporations do that some people do not like.”

The S.E.C. was established in 1934, in the shadow of the Wall Street crash, for the very specific and very important role of protecting markets. It does this, first, through mandated disclosure of corporate earnings, and second through enforcement.

Despite some slips, American securities markets remain the world’s most trusted, mainly because most companies’ operations are accurately represented by their public filings. When the S.E.C. has landed in trouble, it has usually been because it has wandered from its charter and ignored its bread-and-butter responsibility (see Madoff, Bernie). This kind of overreach is, in effect, what Ms. Warren is advocating now in her criticism of the S.E.C. chairwoman.

Instead of involving itself in the politicized issue of campaign spending, the S.E.C. should be thinking about core issues on its own turf. For example, given a spate of judicial reversals of insider-trading convictions, does the agency need a new approach — or should it seek new legislation to combat insider trading? Another: With retail investors flocking to index funds, does the agency fully understand the risks if investors should start to flee such funds en masse? And do investors understand the risks?

In addition to these concerns, the S.E.C. faces continual pressure on its budget from a skeptical and unappreciative Congress. The last thing it needs is political grandstanding from Ms. Warren.