By Jonny Hogg
ANKARA (Reuters) - A grand new palace, toothless opposition and fawning ruling party have helped Tayyip Erdogan craft a powerful role as Turkey's head of state; but elections may yet deny him his goal of a full executive presidency and sow political uncertainty.
Erdogan, accused by critics of suppressing checks to his power in the judiciary and media, said this week the question of constitutional change to cement the presidency should be a central issue in polls to be held by early June.
"The biggest advantage... would be in abolishing policy-making through multiple channels," he said.
Many Turks have vivid memories of fractious coalitions in the 1990s before Erdogan swept to power bringing one-party rule and economic stability. But for opponents, power has become too centralized and the atmosphere poisoned by accusations of graft and purges against perceived enemies in police and judiciary.
With pollsters suggesting the ruling AK Party will struggle to achieve the majority he needs, Erdogan appears to be falling back on "Plan B" - a de facto presidential system analysts say is inherently unstable.
Erdogan was elected president of Turkey, a key NATO ally on the edge of the Middle East, in August after more than a decade as prime minister. He vowed to use his mandate to strengthen what had been a largely ceremonial post and seek constitutional change to shift from a parliamentary to a presidential system.
He has wasted little time flexing his political muscle, hosting his first cabinet meeting as president this month and surrounding himself with powerful advisors some officials see becoming a "shadow cabinet".
That puts him at odds with the spirit of a constitution that says the president must act "without bias" and the tradition of a presidency above politics, according to Fadi Hakura, Turkey expert at London-based Chatham House.
"Erdogan is acting beyond the most liberal interpretation of the constitution," he told Reuters, predicting that cracks could start appearing within the AK Party after the election if roles are not clearly defined.
"The stresses within the system, between the presidency and the ministerial cabinet, will increase with time unless the constitution is changed," he said.
Erdogan, his country buffeted by crises on its border and playing host to nearly two million Syrian refugees, knows the value of political theater.
He recently posed on the steps of his new 1,150-room palace with a presidential guard dressed in costumes from different eras of Turkic history; a display described by Aykan Erdemir, a deputy for the main opposition CHP, as an effort to win over voters on the right.
"He's building the infrastructure, but more importantly he's trying very hard to build the legitimacy of an executive presidency. Symbols are very important."
PREMIER DENIES TENSION
Prime Minister Ahmet Davutoglu denies any tension with the man who towers over the AK Party he founded and was forced by the constitution to leave on taking up the presidency.
"We are from the same political tradition," he said. "In the future, if there is any constitutional change, we will see. But at the moment this is the division of power which is clear from the perspective of legality and...political responsibility."
Erdogan, not known for his tolerance of criticism, dismisses fears parliament could not curb his powers.
"If you are a strong authority, you give the president the power, and then inspect it afterwards."
The AK Party needs a two-thirds majority to change the constitution directly.
Reuters spoke to two pollsters - A&G and Metropoll - who put AKP support at 37-49 percent. That would make them comfortably the biggest party, but well short of the 366 seats needed.
"They're putting a de facto presidency in place knowing full well they probably won't be able to change the constitution," said Aaron Stein, associate fellow at the Royal United Services Institute.
Turkey's position bordering Iraq, Syria and Iran, its presidency of the G20 and the need for cooperation fighting Islamic State militants mean Erdogan's tightening grip may meet little resistance from Western allies.
The Kurdish vote could be key.
Electoral law stipulates a 10 percent threshold for parties to enter parliament. If the pro-Kurdish HDP falls short, its votes would be redistributed proportionally, helping the AKP.
If the HDP reach parliament, the promise of progress in efforts to end a 30-year-old Kurdish insurgency could attract Kurdish support.
Alternatively Erdogan may target the 330 votes needed for a referendum, turning to an electorate which has handed him and his AK Party straight election victories since 2002.
With many of the party's old guard reaching its self-imposed three-term parliamentary limit, Erdogan is expected to exert tight control over their replacements.
"In the first era... loyalty to the "cause" was most important," Murat Yetkin, editor of Hurriyet Daily News, wrote. "In the second era, it seems loyalty to the "leader" will be most important."
(Additional reporting by Humeyra Pamuk and Nick Tattersall in Istanbul; Editing by Nick Tattersall and Ralph Boulton)