Putin might be seen as a 'mad dictator' — but he has built powerful barriers to prevent a coup

If his reputation wasn't bad enough before Russia's unprovoked invasion of Ukraine, President Vladimir Putin is now even more widely seen as unstable, unreliable and untrustworthy — and those are the more generous descriptions of a leader who has ordered and overseen violent and destructive aggression toward Russia's smaller neighbor.

The invasion has prompted analysts and close watchers of Russia to not only question whether Putin has any moral compass, but also his sense of reality, geopolitical strategy and grip on power.

Specifically, many experts are asking whether the invasion of Ukraine — which has had unintended consequences for Russia, leaving it on the verge of economic ruin while uniting most of the international community against it — could backfire spectacularly on Putin, leaving him vulnerable to an uprising at home, as living standards fall, or a coup led from within by members of his political and business elite.

"The solution begins with naming the problem — the problem is a mad dictator which essentially got detached from reality over 20 years in power, and he's absolutely delusional and ready to do whatever he can to destabilize the global order," Vladimir Milov, a Russian opposition politician and former deputy energy minister, who now lives in Lithuania, told CNBC Wednesday. CNBC has requested a response to the comments from the Kremlin and is awaiting a reply.

U.S. President Joe Biden was in hot water at the weekend for suggesting that Putin "cannot remain in power" in Russia, with the White House later walking back those comments, saying it does not endorse regime change.

Milov defended Biden, saying he had only said what everyone is thinking. "Western leaders finally named the problem for what it is, which is Putin continuously staying in power, that's the key challenge for the peace, prosperity and stability of the world."

Putin is widely seen to have derived his power from protecting and enriching a business elite, as well as persecuting Russia's political opposition, among whom the most prominent figure is Alexei Navalny who was imprisoned on what are widely seen as trumped-up charges.

Putin is also said to be surrounded by "siloviki," or "strongmen," who were former colleagues of his in the KGB (the predecessor of the FSB, Russia's security service) or who come from the military and security services such as the GRU (the foreign military intelligence agency) or the FSO — the Federal Protective Service, a federal government agency believed to have around 50,000 personnel who are responsible for protecting high-ranking state officials, the highest being the president.

The FSO includes the Russian Presidential Security Service which is the president's personal security detail. It's reported that the FSO is responsible for the safe passage of the nuclear briefcase — a specially outfitted briefcase used to authorize the use of nuclear weapons.

When it comes to an internal coup, Milov said it was important not to "have some rosy hopes about that" as it would be extremely difficult to overcome the barriers Putin has built to protect himself from being overthrown.

"It's different from Soviet times when we had a more-or-less legitimate governing body like the Politburo that could have deposed the secretary-general. We don't have that anymore, now it's just the president versus a complete vacuum."

He noted that anyone bold enough to try to depose Putin would have to somehow "prove that everyone has to obey his orders." Secondly, Milov said that "everyone is surveilled by the security services 24/7" and that any group of officials "even having a two or three-person gathering" would be suspected and immediately reported.

Milov noted that while relations between different military, paramilitary and security structures were very uneasy, "Putin has his own 50,000-strong security guard which is not governed by anybody else but him and which also incorporates communications so you can't cut him off," he said.

Melinda Haring, deputy director of the Atlantic Council's Eurasia Center, told CNBC on Wednesday that it's extremely difficult to gauge the mood in Putin's inner circle, and within the higher echelons of the military.

"This is a closed political system, Vladimir Putin is very paranoid, very controlled, and we don't know what people are thinking — there are things that have happened that have surprised all of us — there are fuel shortages, there is low morale, the Russians are not prepared and they're not playing their A-game, but the idea that there is going to be a palace coup and the Russian military is going to overthrow Putin? I don't think so, it's very, very unlikely," she said.

Putin's overthrow by members of the security services and/or military is still very unlikely, but analysts have noted that it cannot be excluded if the economic hit from international sanctions becomes too much for many Russians to bear.

If it were to happen, Henry Rome, director of global macro research at Eurasia Group, and his team wrote in a note Tuesday, "our assumption is it would be brought about by displeasure with Putin's prosecution of a losing war and the political and economic isolation stemming from sanctions."

A potential overthrow of Putin could be foreseeable in two scenarios, they noted:

One, in a situation where the conflict reaches an unstable stalemate, with continued, harsh fighting but limited change in territory. In this scenario, Russia would exercise "tenuous control" over most of southeastern Ukraine and parts of central and northeast Ukraine, and while negotiations with Ukraine to find a peace deal would make some progress, they would not yield a diplomatic solution and sanctions would intensify.

In the second scenario, Putin's position could be increasingly vulnerable if he orders an escalation to the conflict in which the Russian forces attack Kyiv and try to exercise broader and firmer control in eastern Ukraine. In this scenario, "sanctions and Western support for the Ukrainian military escalates [and there are] broader macroeconomic consequences, especially in Europe." This scenario could also see direct NATO-Russia air combat above Ukraine's borders, the analysts noted.

In both these scenarios, Putin's overthrow could follow if Russia's elites are convinced that "Putin risks disaster for Russia and for them personally."

Russia is widely believed to have expected an easy victory when it invaded Ukraine. But the conflict, now into its fifth week, has been anything but with Russian forces facing a quagmire in many parts of the country.

Although Russian forces look set to seize the southern port city of Mariupol, which has been under siege for weeks and staunchly defended by Ukrainian fighters, so far Russia has only captured the city of Kherson and even its hold on that looks shaky. There, as elsewhere, Ukrainian forces have started to launch counterattacks to repel Russian troops in a significant fight-back that has dented Russia's manpower and military ability.

There are expectations now that Russia could look to secure a deal with Ukraine in order to save face, and to be able to claim some kind of victory back home, as a wider occupation of Ukraine and regime change in Kyiv look like impossible objectives.

"Putin's image as a tactical/strategic genius is in tatters," Timothy Ash, senior emerging markets sovereign strategist at BlueBay Asset Management, said in emailed comments Tuesday.

"In the run up to the war the main argument used by the Kremlin to explain why they would not wage war in Ukraine was because they were not that stupid to do exactly what the Yanks wanted them to do, and get dragged into a war in Ukraine, similar to those waged by the U.S. in Iraq and Afghanistan. Guess what, Putin really was that stupid. Even more stupid, as despite knowing the risk, he still did it."

Ash said that the way Russia has conducted this war, launching an unprovoked attack on a sovereign nation and conducting indiscriminate bombing of cities and civilian targets, has made Russia and Putin "international pariahs, and likely for long to come."

"The reputational damage has been immense," he noted.