Because of the wide latitude allowed, sunlight is deemed the best disinfectant. Since 1978, senators have been required to disclose all their personal financial holdings (and those of their spouses and dependents) in an annual Financial Disclosure Report (FDR). This yearly exercise is considered the most effective mechanism for deterring gross conflicts of interest or egregious self-enrichment.

The supposed transparency of the FDRs, however, is not all that it is cracked up to be. And this is the other troubling aspect exposed by the new study. The trading data available in the FDRs presented a host of problems. While some senators simply attached the monthly financial statements from their brokerage firms to the FDR, others provided only handwritten notations or abbreviations that the professors found impossible to decipher.

More significantly, senators are only required to report their gains within eleven broad bands ($1,001 to $15,000, $15,001 to $50,000, and so forth), and so the exact amount of their profits cannot be measured. In order to perform their analysis, Ziobrowski and his fellow professors had to create imaginary portfolios that mimicked the buy-and-sell transactions the senators engaged in. While this methodology in no way invalidates the study's key finding, it dulls the political point with respect to specific senators when a dollar amount cannot be attached.

Indeed, the "banding problem," as it's known to money-in-politics cognoscenti, is a serious defect in the FDRs because it obscures almost as much as it reveals. One member of Congress, for instance, listed assets, in bands, that totaled somewhere between $813,000 and $1.7 million in 1996. This same member, nine years later, listed assets totaling somewhere between $2.4 million and $8.1 million. The gap between those numbers suggests two very different portraits: a member who is either simply a prudent investor, or someone who rivals Warren Buffett, albeit by exploiting, in all likelihood, the boundless perks available to elective officeholders. These opportunities encompass everything from getting in on the ground floor of initial public offerings of stock, to sweetheart real-estate deals. Ted Stevens once turned a $50,000 investment with an Anchorage real-estate developer into $1.03 million in seven years.

Senators' ability to time the stock market is one reason why at least 60 senators are worth at least $1 million now. As recently as 1994, only 28 senators had a net worth of that amount or more, and their salaries (currently $162,100) have not gone up fast enough in that 11-year period ($28,500) to account for this increased wealth.

THE LOWDOWN ON THE "UPPER BODY"—The Senate, of course, has always had its share of members unable to distinguish between their own personal fortunes and the nation's. The late Robert Kerr (D-OK), the "uncrowned king of the Senate" in the 1950s, comes to mind. Born in a log cabin, but the wealthiest man in the Senate by far during his years of service, Kerr was infamous for privileging oil and gas interests, including his own company (Kerr-McGee), from his perch on the Finance Committee. Kerr believed doing business in the Senate was no different than doing business on the outside: Everything was predicated on a quid pro quo basis.

Besides venal members, the Senate has always had its fair share of "empty suits," senators whose main qualification is that they look or sound like Central Casting's idea of a senator, as well as more than its share of ambitious politicians who regard the upper house primarily as a steppingstone. But what seems different now, and what makes these charming peccadilloes and real shortcomings harder to swallow, is that so few senators seem capable of, or committed to, fulfilling their responsibilities as public servants. Seldom in its history has the Senate seemed so removed from what the Founding Fathers envisioned: the place where the power of the executive branch and House could be checked, and the forum for "express[ing] sober second thought on national priorities," as Lewis Gould put it in his recent history of the Senate, The Most Exclusive Club.

The restraint of executive power has seldom been weaker. During the last decade, under Presidents Clinton and Bush, and without a declaration of war, the U.S. has bombed Serbia's Slobadan Milosevic into submission; toppled the Taliban in Afghanistan; and instigated a war of choice to overthrow Iraq's Saddam Hussein. Towards the end of the Vietnam War, the 1973 War Powers Act was put in place to check the commander-in-chief's ability to commit American lives and treasure; the Senate spearheaded passage of the act. Although largely symbolic, it at least held out the promise of forcing meaningful debate over the issue of war. But nowadays the Senate is likely to give a transportation bill more thoughtful deliberation than a decision to commit American soldiers, as Leslie Gelb and Anne-Marie Slaughter noted in a November article in The Atlantic. Reportedly, only six senators read the classified intelligence estimate on Iraq before voting to authorize the use of force there.