Donald Trump's decision to fire FBI Director James Comey this week might well be the single most damaging event so far of a presidency that has been defined by unrelenting chaos since its first day of existence. Sprung on the country with so little warning that even the White House's own press shop was caught completely unprepared to address the subject, the Comey sacking was accompanied by a public justification so completely implausible that Trump's own aides readily conceded its falsity to the press once guaranteed anonymity. It was immediately obvious that Trump's action was not motivated by a desire to avenge the unfair treatment of Hillary Clinton but was instead intended to squelch the FBI's investigation of his own campaign's ties with Russia—inspiring a plethora of comparisons to Richard Nixon's "Saturday Night Massacre" and raising dark musings about obstruction of justice and other impeachable offenses.
Axing Comey was a bungle of multi-dimensional proportions. Trump may have been sick of hearing about Russia every time he turned on the television, but his "solution" to this particular problem merely ensured that cable news will talk about little else for weeks or more. Making enemies in the FBI also increases the probability that damaging information winds up leaking to the media, and any indication that pressure from the top has indeed attempted to curtail the Russia probe will set off a ten-ton explosion inside the Justice Department. It also makes the president look as if he is guilty of a serious offense—whether or not he actually is.
One might expect congressional Republicans to distance themselves as much as possible from the Comey affair, if only for the purposes of political self-preservation. With a few exceptions, however, party members have remained supportive of Trump's decision to fire Comey and dismissive of suggestions that the circumstances warrant the appointment of a special counsel or formation of an independent investigatory commission. House Speaker Paul Ryan characterized Trump's action as "an important command decision" and argued that "it was entirely within the president's role and authority to relieve" Comey. Senate Majority Leader Mitch McConnell similarly rejected Democratic calls for a special prosecutor on the Senate floor Wednesday morning, suggesting that the entire controversy was merely an exercise in partisanship.
It's likely that most Republicans in the House and Senate privately view the Comey firing as a mistake on Trump's part, and may even worry that the new president will continue to lurch from one self-made crisis to another over the next 18 months. But that doesn't necessarily mean that they think creating daylight between Trump and themselves would work to their own benefit. Republicans commonly view the successful mobilization of their own party's conservative base as the decisive factor in elections, rather than courting of the independent or swing vote. Under this theory, turning against Trump—no matter how much his behavior might justify it—only hurts the congressional party by reducing the enthusiasm of Republican voters for showing up at the polls in 2018 and 2020.
McConnell in particular believes that voters are persuaded more by partisan cues than by objective facts. His openly-acknowledged justification for preventing any bipartisan agreement on health care reform during the Obama administration was that bipartisanship "tend[s] to convey to the public that this is OK, they must have figured [the issue] out," resulting in broad popular support. In other words, voters are significantly more likely to approve of a policy endorsed by members of both parties than an identical policy over which Democrats and Republicans remain divided—which means that one's own party should avoid conceding ground to the positions adopted by its opponent whenever possible.
To McConnell, Republican support for any Democratic calls to investigate Trump would only signal to voters that Trump had indeed done something wrong, further reducing the president's public support and thus giving the Democrats even more of an advantage. Converting every Trump-related controversy into a partisan food fight instead allows Republicans to summon their base to rally behind them in yet another polarizing battle against the left. Since Democratic supporters are already likely to be highly motivated to turn out against Trump in the next two elections, Republicans are concerned about whether their own side will match their opponents' level of engagement.
Of course, this approach carries certain risks. The most obvious danger is that congressional Republicans could wind up chaining themselves more tightly to Trump just as he plummets off a political cliff. The lack of a meaningful difference between Trump and the rest of the Republican Party gives anti-Trump voters good reason to replace even personally popular Republican incumbents with Democratic challengers. Unless Trump finds a way to bolster his national popularity in the future, even a relatively energized Republican base may not be enough to protect the party against a wider popular backlash among Democrats and independents.
It's also quite possible that Ryan and McConnell would be better served in the long run by buzzing a warning pitch or two under Trump's chin at this stage of his presidency. Automatic party support for his various antics in office may only reinforce bad behavior on Trump's part, making future Comey-scale debacles all the more likely and dragging the entire party into an inescapable political morass. Occasional demonstrations of independence by congressional Republicans might have a constraining effect on a president with flawed knowledge, instincts, and judgment, encouraging him to consult with a wider array of interlocutors and steering him away from the most disastrous courses of action. Normally, party leaders' interests are not well-served by greater intra-party tension. But we are, at the moment, a fair ways off from normalcy.