What is it about presidents' second terms that makes them seem so scandal-ridden? Simple: The iron law of longevity. All governments make mistakes, and all governments try to hide those mistakes. But the longer an administration is in office, the more errors it makes, and the harder they are to conceal.
Just ask Richard M. Nixon, Ronald Reagan, Bill Clinton or George W. Bush, all of whom spent much of their second terms playing defense.
The longevity rule caught up with Barack Obama last week as he wrestled clumsily with not one controversy but three: the Internal Revenue Service's treatment of "tea party" groups, the Benghazi killings and the Justice Department's seizure of Associated Press telephone records.
Inevitably, the president's Republican critics reached for historical comparisons: It's another Watergate, said some. Another Iran-Contra, said others. To the hyperbolic Rep. Steve King of Iowa, Benghazi alone was worse than Watergate and Iran-Contra combined, "times maybe 10."
So far, though, the three imbroglios don't add up to another Watergate; not even close. But there are enough unanswered questions to keep any administration tied up for months in congressional hearings, and that's exactly what's about to happen.
Let's take the three issues in turn.
The IRS scandal is the most straightforward: A mismanaged unit of the tax agency applied political criteria to its scrutiny of applications for tax-exempt status. Despite the initial portrayal of a rogue operation confined to Cincinnati, IRS officials in Washington knew about the problem and failed to fix it. At least one appears to have misled Congress last year by suggesting that tea party complaints were unfounded.
Last week, Obama condemned the IRS conduct as "intolerable and inexcusable," and he fired the agency's acting director.
But every customer of the IRS, not only Republicans, should want an independent investigation to determine whether higher-ups encouraged the Cincinnati cabal.
Benghazi is the most tangled issue, and the most partisan. A State Department review board has already concluded that security for Ambassador J. Christopher Stevens' fatal visit to the Libyan city was inexcusably weak; then-Secretary of State Hillary Rodham Clinton accepted responsibility for that.
But the political side of the Benghazi "scandal," which still needs to be in quotes, has focused on other targets. Republicans charge that Obama lied about the attacks, portraying them as spontaneous to avoid weakening his election-year claim that he had put Al Qaeda on the path to defeat.
It's true that Obama was slow to blame terrorists for the killing. "We don't have all the information yet," he said on Sept. 25. But by then, other officials had already told Congress that Al Qaeda affiliates were involved. That was five weeks before the election; if the White House was trying to mount a coverup, it apparently forgot to tell the rest of the administration.
It's also true that Obama aides presided over an internal debate over what information would be in official talking points. But when the White House finally released emails from that wrangle, they mostly revealed a bureaucratic fight between the CIA, which wanted to trumpet its warnings about Libya, and the State Department, which didn't want to expose its failings. There's no evidence of anyone acting to protect the Obama reelection campaign.
Still, the White House has a problem: It's been acting guilty. Obama spokesman Jay Carney said initially that the White House had little to do with the talking points, and that only one substantive change was made to the text. Those descriptions turned out to be false. It's no wonder Republicans have demanded more answers. But the Benghazi talking points still look mostly like a partisan sideshow, too complicated and murky to engage most voters.
The third controversy, over the Justice Department's secret decision to seize telephone records of dozens of reporters and editors at the Associated Press, is a different kind of scandal. Republicans have been careful about this one because many have long demanded that the Obama administration get tough on leaks of classified information.
But it still fits into the GOP's critique of Obama as imperious and authoritarian. And it puts another dent in Obama's already battered image as a onetime civil libertarian who has grown fond of executive power in office.
If Obama is both smart and lucky, all three controversies will gradually fade away, assuming no more wrongdoing comes to light. His Republican critics already run the risk of repeating their error in the 1998 impeachment of Clinton; if they hound the White House on charges that don't pan out, they'll be vulnerable to charges that they're wasting time on partisan squabbles.
During the Monica Lewinsky scandal, the Clinton White House made a point of putting the president on camera every day to show he was at work on the economy, not his legal troubles. The Obama White House is already following the same path.
But a season of scandal still comes with a cost. If Congress spends much of its time on investigations (and one-third of all House committees have announced they plan to do just that), it will have fewer hours to work on other issues. If the White House must focus on defending the president against charges of malpractice, that saps its energy as well.
Any second-term president has limited time after reelection to win legislative battles. Obama's clock is already ticking; his agenda is already in trouble. If the remainder of 2013 is dominated by inquests that widen the partisan divide, the chances for bipartisan deal-making — especially a grand bargain on taxes and spending — will wane even further.
Follow Doyle McManus on Twitter @DoyleMcManus