(CNN) Even as Donald Trump swerves from one stunning headline to the next, his presidency is firmly planted on this rock-steady subtext: As long as Republicans in Congress support him, he is essentially invulnerable to blowback from even the most politically reckless behavior.

Like it or not, Republicans on Capitol Hill control both houses of Congress and so are the ultimate arbiters of Trump's fate. Democrats can try to gum up the works, create a further sense of crisis and, over time, use it all as part of a strategy to reclaim power. But even if they execute it all perfectly, 2018 (well, January 2019) is a long way off. For now and the foreseeable future, Washington belongs to the GOP. Nothing changes in a meaningful way unless they want it to.

As it stands, Democrats simply want to force the appointment of a special prosecutor to conduct a nonpartisan Russia investigation. Senate Minority Leader Chuck Schumer said he'll try to block any new FBI director until a special prosecutor is named.

But he can't do it alone . Schumer would need two Republicans to break ranks, likely against the explicit wishes of their party leaders. It's an obstacle he noted during an interview over the weekend.

"To have that special prosecutor, people would breathe a sigh of relief, because then there would be a real independent person overlooking the FBI director," Schumer said on CNN Sunday. "The key here, of course, is getting some of our Republican colleagues to join us. We're hoping. We're waiting. We understand it's difficult, but I think patriotism and the needs of this country demand it."

So for all the hysteria that followed Trump's decision to fire FBI Director James Comey last week, the fundamental logic of this presidency, along with the interests that guard it, remain firmly in place. There is no reason, at least none we're aware of at this day or hour, to suspect it is going to change anytime soon.

Implicit in the GOP's decision to back Trump during the general election campaign were two expectations, or hopes. First, that he would "pivot" and, with more power, would become more reasonable. That he would mellow out on Twitter and hunker down on policy. The other cast him as a rubber stamp on Republican policy, pushing to repeal Obamacare and lower taxes. On the second count, the President has done his part.

JUST WATCHED McConnell admonishes Democrats over Comey Replay More Videos ... MUST WATCH McConnell admonishes Democrats over Comey 01:22

In the immediate aftermath of Comey's dismissal, there emerged a sense -- perhaps a hopeful one fueled by Trump's stalwart critics and opponents -- that the game had changed. This misunderstood some very basic things about power and history.

First though, a word about Comey. Don't underestimate what a mess the President has created. The White House's priorities, however you want to rank or articulate them, are stalled. Congressional Republicans, on the march after squeezing their Obamacare replacement through the House, now have another angry river to cross . Individual senators and members of Congress are reportedly anxious over what comes next. Their confidence in Trump is diminishing

Looking back on the last seven days, a few things become clear. There was no logical -- that is, politically rational -- explanation for the firing. Trump and his staff offered a variety of answers, but to this day haven't settled on a single one. In the end, it boils down to this: Comey was fired either a) because Trump wanted to short-circuit an investigation focusing at least in part on his own campaign's alleged ties to Russia or b) because Trump, in a pique of anger, lashed out at one of the people he blamed for, in his estimation, undermining the legitimacy of his election victory.

That's where we're at. History tells us a lot about what comes next. Trump's behavior has invited countless comparisons to Richard Nixon's, especially during some of the darkest hours of the Watergate scandal. The abrupt sacking of a top federal law enforcement official made for some easily (perhaps too easily) drawn parallels. Trump like Nixon seems beset by paranoia, loathing and contempt for the press and even loyal political opposition.

JUST WATCHED Comey's firing compared to Nixon 'massacre' Replay More Videos ... MUST WATCH Comey's firing compared to Nixon 'massacre' 01:13

But there is one very important difference, one that gets lost in the Watergate hoopla. Unlike Nixon as he neared the abyss, Trump now retains the support of Republicans in Congress, and those Republicans control the place. Whatever their personal feeling about the man in the White House and despite any concerns they might harbor about his fitness, not a single elected GOP official on Capitol Hill has rejected Trump outright. Even those who criticized the Comey firing left themselves more than enough room to come back home when the fever breaks.

Nixon, on the other hand, had by the last year of his presidency lost control of his own party and was up against a Congress controlled by the opposing party. As the Supreme Court stepped in to order he turn over the White House tapes once sought by (and denied to) a special prosecutor, Congress, controlled by Democrats, was preparing for its first debate on articles of impeachment . Would Nixon have complied with the court, narrowly avoiding an actual constitutional crisis, if there had not been a bipartisan group down the street readying the gallows? At the very least, the decision would have been more difficult.

And so it goes with Trump. With Republican majorities in his corner, there is no meaningful check on his day-to-do behavior. If he's taken anything from the first week of the post-Comey era, it could easily be that, "Hey, I can fire someone investigating me (again), and my friends in Congress, the ones who aren't defending me, might chirp a bit, but that's all."

It's not that nothing matters. It's that nothing changes until and if Republicans turn on Trump. For all the hysterics, the only base of support that, if compromised, could endanger his presidency, is on Capitol Hill. As long as the GOP controls both chambers and backs the Trump publicly, there's little to compel him to change. And in the case of further conflicts, to back down.