At first glance, Russian president Vladimir Putin seems to have defied all the odds.

Russia is poised to mount a winter offensive against a defiant Ukraine that still struggles to supply its army, treat its wounded and repel a world military power. In November, international monitors sighted more convoys of Russian vehicles carrying soldiers, as well as unmarked T-72 and T-64 tanks, crossing from Russia into eastern Ukraine near Donetsk.

An October poll indicated the Russian president has an 88-percent approval rating. Politically, he seems unassailable.

That could be changing. As Ukraine grows more defiant and Russia’s economy suffers, more and more Russians are losing interest in Putin’s war.

At the moment, there is no apparent political rival with the ability to challenge Putin’s policies or his rule. To further consolidate his power, Putin has jailed dissenting journalists and opposition politicians.

The United States and the NATO alliance don’t want a direct confrontation with Russia over Ukraine, instead relying on sanctions and rhetoric that mostly have done little to trouble Putin or his supporters among Russia’s elite.

But now increasing economic doldrums—owing to collapsing oil prices and a devalued ruble—plus fervent Ukrainian nationalism and a Ukrainian army that prevails despite its immense problems, indicate Putin’s future might not be as rosy as his recent years.

There have even been a few scattered near-mutinies among Russian troops resisting deployment to eastern Ukraine.

“Although Putin is in a strong position now, he’s replaceable,” Graeme Auton, professor of political science at the University of Redlands and an expert on Russian energy policy, told War Is Boring. “I think he is in an increasingly tenuous position, and he is facing what is for him an unfortunate confluence of events.”

Consider the recent drop in oil prices. As Putin continues the invasion of Ukraine, OPEC dealt an economic body-blow to a nation where oil revenues comprise nearly 50 percent of the Russian budget annually—a loss of at least $100 billion according to some estimates.

In addition, the ruble continues to plummet in value against both the dollar and the euro. Against the dollar, the ruble has lost nearly 30 percent of its value during 2014 alone.