Some call him Turkey's ultranationalist kingmaker, others see him pulling the strings of the state's security policy.

Yet for a man whose far-right MHP party won only 11 percent in a 2018 election, Devlet Bahceli's influence over the government stretches far wider than his vote share.

Now, with support for President Recep Tayyip Erdogan's AKP party slipping, the Turkish leader may need Bahceli's MHP more than ever to extend his rule into a third decade.

Balding, diminutive and craggy-voiced, the 73-year-old Bahceli cuts a mysterious figure despite leading the MHP since 1997.

Critics say Erdogan does Bahceli's bidding in return for votes that guarantee the government a parliamentary majority, steering Turkish policy ever further to the right.

When the coronavirus became a grave issue last year, Bahceli secured the release of a mafia boss he knew as part of an early release amnesty for prisoners.

"In the past three years, Mr Bahceli's attitude and behaviour have set the AKP's political course," said Idris Sahin, a former AKP member who is now the deputy chair of the opposition DEVA Party.

"So despite having little representation in government, the MHP's influence is just as big as that of the AKP," Sahin told AFP.

The MHP has no government ministers, although the nationalist-leaning Interior Minister Suleyman Soylu is a party favourite.

When Soylu tried to resign last year because of his handling of Turkey's first coronavirus lockdown, Bahceli and the MHP rallied to his defence.

Erdogan rejected the resignation, and the interior minister is now politically stronger than ever.

Bahceli's influence was again on show after a top court's chief prosecutor filed a case last month to shut down the country's main pro-Kurdish party.

He had led the closure calls, and the case was announced the day before an MHP party congress, viewed by critics as Erdogan's "gift" to his partner.

The MHP acts as Turkey's "national security council", associate professor Burak Bilgehan Ozpek said, referring to a once-powerful body filled with military figures.

"The MHP draws the national security policy framework," Ozpek said, adding that Bahceli can decide whom to designate as terrorists in Turkey.

When a leading AKP figure objected to banning parties in December, Bahceli countered that the issue was about "punishing treason".

"It's important for Bahceli that the AKP acts in line with the national security framework," Ozpek told AFP.

Balding, diminutive and craggy-voiced, 73-year-old Devlet Bahceli is the leader of Turkey's Nationalist Movement Party
Balding, diminutive and craggy-voiced, 73-year-old Devlet Bahceli is the leader of Turkey's Nationalist Movement Party AFP / Adem ALTAN

Yet the AKP, which is rooted in political Islam, and the MHP come from different backgrounds and Bahceli has not always gotten his way.

He was a supporter of an oath students recited in school, which included the nationalist line: "I'm Turkish. I'm right."

The AKP ordered its removal from schools in 2013, a decision a top administrative court approved in March.

The MHP's "People's Alliance" with the AKP only happened after Bahceli had at first opposed Turkey's transformation from a parliamentary republic into an executive presidency.

But he changed his mind after a failed overthrow of Erdogan in July 2016. The shift was approved by the public in a referendum and came into force in July 2018.

"For our country's survival, the People's Alliance became a necessity," said MHP lawmaker Ayse Sibel Ersoy.

"That is how the MHP and the AKP came together," Ersoy told AFP.

The MHP's backing for the new system opened the door for their ultranationalist supporters to enter the state bureaucracy, according to academic Berk Esen.

"Under the presidential system, the MHP has increased its importance, there's no question about that," the assistant professor at Sabanci University said.

There is still some disagreement between analysts and Western diplomats over the extent to which Bahceli actually controls Erdogan.

"Erdogan has to keep the alliance going but the president is constricted by Bahceli," said a Western diplomat.

After discarding previous allies, including Western-leaning liberals, Erdogan is left with the ultranationalists.

But Esen said Erdogan still had "the upper hand" over Bahceli.

"I don't think Erdogan has been led astray and is forced to take steps that he doesn't really want to," Esen said.

Another Western diplomat described Bahceli as a kingmaker, a description Ozpek of TOBB University disagreed with.

"Turkish politics' kingmaker is Erdogan. Bahceli plays this role because Erdogan allows him," he told AFP.

"Bahceli can speak as if he is the national security council because Erdogan benefits from this. Erdogan doesn't want to stop him."