Mikheil Saakashvili, center, finds himself locked in a bitter battle with Ukraine’s president, Petro Poroshenko. (Franko/Epa-Efe/Rex/Shutterstock/Franko/Epa-Efe/Rex/Shutterstock)

They call him "the Energizer Bunny."

To his supporters, Mikheil Saakashvili, the former Georgian president, is a tireless warrior against corruption and Vladimir Putin's Russia who transformed his graft-ridden country into a showcase for Western reforms and is one of the most charismatic figures in the post-Soviet sphere.

To his enemies, of whom there are many, he is a confrontational and divisive showboat who has a predilection at times toward authoritarianism and is consumed with a lust for power.

But both sides agree on one thing: He doesn't give up a political fight.

Today Saakashvili finds himself locked in yet another bitter battle — in Ukraine. And his main target is an old friend from his university days in Kiev in the late 1980s: the country's president, Petro Poroshenko.

Saakashvili's biography has seen numerous turns. A graduate of Columbia Law School, he spearheaded Georgia's 2003 "Rose Revolution" and became a poster boy for the Bush administration's international pro-democracy agenda. (The U.S. Secret Service first gave him the "Energizer Bunny" moniker.) He built a glass-walled police headquarters in Tbilisi to underscore his commitment to molding a modern and transparent force.

But in 2008, he fought a disastrous war against an invading Russian army. He left office and his country in 2013, after his term ended and his party lost power.

After living briefly in Brooklyn, he moved to Ukraine and, at Poroshenko's invitation, became the governor of the Odessa region.

That didn't last, and now he has recast himself as a leader in Ukraine's anti-government opposition.

This month, he has organized a pro-reform occupation of sorts in front of the country's parliament.

"Throw the goat out!" Saakashvili said in reference to Poroshenko, whom he accuses of corruption and blocking reforms to protect his allies. Later, he called the Ukrainian president "a cheap Mafioso."

The government is fighting back. This year, Ukrainian authorities said Saakashvili incorrectly filled out his citizenship application, and they stripped him of the Ukrainian passport he obtained in 2015, barring him from entering the country. (He was in the United States at the time of the announcement.) The move drew heavy international criticism and rendered Saakashvili a stateless former head of state, since Georgia had revoked his passport when he received Ukrainian citizenship.

In September, Saakashvili responded by storming through a border crossing into Ukraine with hundreds of his supporters. He subsequently announced a "united opposition" against Poroshenko and barnstormed the country to garner support and raise his profile.

But the story is far from over — and Poroshenko may have the last word.

Last week, Ukraine's prosecutor general, Yuri Lutsenko, a Poroshenko ally, announced that authorities had rejected Saakashvili's petition for political asylum, opening up his possible deportation to Georgia, where he is wanted on charges of embezzlement and abuse of power while in office. Saakashvili says the case against him in Georgia is a political witch hunt.

Lutsenko also accused Saakashvili of trying to organize "a violent coup" and obtaining visas for 20 of his Georgian supporters under false pretenses. Saakashvili, for his part, denied the accusations and said authorities had illegally seized and deported a number of his followers.

"The general prosecutor is lying completely!" Saakashvili wrote in a Facebook post, claiming that Ukrainian law allowed him to stay in the country.

For Saakashvili, deportation would be an ignominious end to what was supposed to be his political resurrection. When he arrived in Ukraine over two years ago as an exile, Poroshenko installed him as Odessa governor in hopes that the Georgian could work his reformist magic on one of Ukraine's most corrupt regions.

"Mikhail Saakashvili is my friend from our student years. I remember him as a strong and decisive person, and I have reason to trust him," Poroshenko tweeted at the time.

The trust, however, soon turned into open antipathy. Saakashvili said the Kiev government was impeding his reforms and resigned as governor one year later, lashing out at Poro­shenko and other top officials. He launched his own political movement and started a talk show. On one episode, a female war veteran sang a song called "The Chocolate Ass." Few missed the reference: Poroshenko is a billionaire candy tycoon.

But there are political figures, including within the opposition itself, who are uncomfortable with Saakashvili's emergence as a Ukrainian rabble-rouser — the demonstration in front of the parliament being a case in point, they say.

The protest's planners say it was supposed to be short-term and limited to pressuring deputies to adopt three pieces of reform legislation. But Saakashvili and his followers — many of whom were battle-hardened veterans from Ukraine's war in the east with Russian-led separatists — created a military tent camp, complete with field kitchen.

Saakashvili raised the pressure by issuing an ultimatum to Poroshenko to pass the legislation or resign. Clashes broke out between protesters and the riot police who had set up a cordon around the encampment.

"Saakashvili made the protest be against Poroshenko — he personalized it, which is in Saakashvili's interests," said Alyona Getmanchuk, director of the think tank New Europe Center in Kiev.

Only a handful of activists are camping at the parliament, and Saakashvili's polling numbers are still low — below 2 percent — but there's a fear that his go-for-broke approach could delegitimize the opposition as a whole. Some worry it could further undermine the stability of a country still recovering from its 2014 revolution, and battling a stubborn insurgency in the Donetsk and Luhansk regions.

"He's more radical," said a Ukrainian opposition leader who spoke on the condition of anonymity because of the sensitivity of the subject within the anti-government forces. "I wouldn't exclude his resorting to force — a quiet battle would be death for him and his supporters."

In an interview in the offices of his political party, the Movement of New Forces — with a bust of Ronald Reagan next to his desk — Saakashvili, for his part, denied he is seeking confrontation. But he freely admitted to being an egomaniac. "Every politician is an egomaniac," he said with a laugh, claiming that he has mellowed over the years.

"You cannot have all or nothing," he said. "Jackpots no longer interest me in politics, because I also see the risks. You can lose everything."