At least consequence of the president's decision to fire Federal Bureau of Investigation Director James Comey is clear: The investigations of possible ties between the Trump campaign and Russia by the Senate and House intelligence committees will be followed even more closely.
And, if history is a guide, that's bad news for President Donald Trump.
"Increased investigative activity in the hearing room significantly decreases the president's job approval rating," wrote political scientists Douglas Kriner of Boston University and Eric Schickler of the University of California–Berkeley in their 2014 study, published in the Journal of Politics.
In their research, Kriner and Schickler also provide evidence that this effect is greater when Congress is controlled by the president's party. Given that "a wealth of research has demonstrated that low approval ratings make it more difficult to pursue their policy and political agendas," this is no small matter.
The researchers drew these conclusions from both a historical analysis and the results of their own experiment. Utilizing data from the Congressional Information Service covering the years 1953 to 2006, they found 3,507 hearings "that constituted committee investigations of alleged misconduct by the executive branch."
They reported that, after taking into account certain factors known to drive presidential approval (such as the state of the economy), such hearings significantly shift the public's view of the chief executive.
"Increasing the number of days of investigative hearings in a month from zero to 20 decreases presidential approval by about 2.5 percent," they wrote. "This suggests that sustained congressional investigative activity over time has the potential to seriously diminish a president's well of popular support."
To determine if these drops were unique to congressional hearings (as opposed to media accounts of possible misconduct), Kriner and Schikler conducted an experiment in April of 2011. The participants—1,167 American adults recruited on Amazon's Mechanical Turk website—were informed that "Under President [Barack] Obama, the Environmental Protection Agency has prepared new regulations to curb the emission of greenhouse gases."
Some participants were also informed that the Democratic-controlled Senate Energy and Natural Resources Committee "is investigating allegations that the Obama administration has abused its regulatory powers to dramatically expand the power of the EPA." Others were presented with identical language, except that the committee was controlled by Republicans.
Another group of participants was informed that "some political observers" had accused Obama of abuse of presidential power. All participants were then asked how strongly they approved or disapproved of the president's performance in office.
Members of a control group, who receive no information about possible presidential abuse, gave Obama an approval rating of 48 percent—very close to the average of public-opinion polls for that week. The number among those who learned that "some political observers" had concerns was virtually identical—47 percent.
However, Obama's approval rating fell by 5.5 percent among those told he was being investigated by a Republican-led congressional committee. And it plummeted 8 percent among participants told he was being investigated by a committee led by Democrats.
It appears people grow wary whenever there's a congressional investigation of the president, but it really raises alarm bells when the committee is led by a member of the president's own political party.
Of course, Trump is an outlier in many ways. It's possible that his strongest supporters are so committed to him that this dynamic won't be as pronounced this time around. But his overall approval ratings are historically low, meaning he can hardly afford any additional decline.
"Investigations may rarely formally compel presidents to adjust their behavior," Kriner and Schickler concluded. "Yet our results show that they do consistently weaken the president by undermining his reservoir of public support."