Greater than the risk of being accused of criminality in the three scandals now gripping the Obama administration is the peril that the president's substantive agenda is being hopelessly knocked off track.
The liberal Illinois senator who entered the White House four years ago determined to change Washington's ways of doing business still finds himself striving to overcome barriers constructed by the opposition party in Congress.
In his first term, congressional Republicans embraced partisanship straightaway, particularly in the House after they gained a majority there, openly declaring their intent to block his every initiative. Senate Minority Leader Mitch McConnell's goal to make Barack Obama a one-term president became the Republicans' battle cry.
That strategy of legislative obstruction clearly worked in denying Mr. Obama much domestic achievement beyond enacting his major health-care reform law. But even that bitter fight consumed so much time and energy that little else of historic significance was accomplished. In the end, though, GOP stonewalling failed to defeat him last November.
Now, with his second term barely under way, the barrier to an impressive Obama legacy is not so much congressional obstruction as it is congressional investigation. Opposition lawmakers have seized on perceived evidence of administration deception or just dissembling in the IRS, Justice Department and Benghazi fiascos, throwing the man in the Oval Office into damage control mode.
Congress, in turn, has gone into investigative mode, using its subpoena powers and public concern over executive branch ineptitude or arrogance (or both) to put the president and his subordinates on the griddle. The administration's explanations have already fueled the impression that the president either didn't know what was going on in his own official household or was being protected from culpability.
Congressional investigations often determine responsibility for wrongdoing and lead to corrective action, not simply in catching an officeholder with his hand in the cookie jar but also in producing a legislative remedy. A prime exhibit was the Senate Watergate hearings of the early 1970s, which ensnared a lying Richard Nixon and collaborators in the cover-up of the infamous break-in of the Democratic National Committee and associated crimes.
At the same time, such investigations can be exploited for partisan objectives in the hands of lawmakers so inclined. For one thing, the device of televised congressional hearings can easily become magnets for self-serving or partisan showboating by legislators converted by the proceedings into prosecutors. Questions routinely are asked not only to elicit information but also to score political points, their purpose easily ascertainable by the party label of the interrogators.
Past congressional investigations going back to the anticommunist witch hunts of the McCarthy era have demonstrated that the power of Congress to compel testimony from executive branch officials can be a two-edged sword. Their ultimate legal protection is the Fifth Amendment guarantee that no individual "be compelled in any criminal case to be a witness against himself."
In that earlier period of legislative warfare against the executive, McCarthy repeatedly equated "taking the Fifth" with an act of disloyalty or an admission of guilt, labeling users of the protection "Fifth Amendment communists." That specter resurfaced this week when former IRS official Lois G. Lerner, head of the unit engaged in political policing of applications for tax-exemption status, invoked the protection against self-incrimination.
Her right to claim the protection was challenged on grounds that she had already opened the door to committee interrogation by offering a statement denying any wrongdoing. She left the hearing room facing the prospect of being called back.
The chairman of the House committee involved, Rep. Darrell Issa of California, has already earned a reputation as a politically motivated congressional sleuth comparable to Joe McCarthy himself, an appraisal sometimes meant as a compliment and sometimes as a condemnation.
A Congress once again seized by investigative impulse augurs only more threats to Mr. Obama's second-term agenda. He must cooperate with the congressional investigators but not allow the most partisan of them to deter him from pursuing his own efforts to right the still-sluggish economy, on whose fate his presidential legacy ultimately will rest.