By Robin Emmott and Francesco Guarascio
BRUSSELS (Reuters) - Turkey's election on Sunday could mark a turning point in relations with the European Union, either bolstering President Tayyip Erdogan's bid to accumulate more power or putting a check on a leader many in Europe accuse of creeping authoritarianism.
The country's second general election in five months comes at a critical juncture for Brussels, which is dangling the prospect of a relaunch of stalled EU membership talks in front of Turkey in return for its help in dealing with the biggest migration crisis the continent has seen since World War Two.
While wary of his authoritarian tendencies, some European leaders have displayed a pragmatic new approach towards Erdogan in recent weeks, appearing to set a deal on refugees above concern about worsening in human rights. Fears about security in a NATO state bordering Syria and Iraq also loom large
Challenging Erdogan "will achieve nothing at the moment" Europe's chief executive Jean-Claude Juncker told the European Parliament this week, a striking shift that has been evident since Erdogan was received with all the pomp of a royal state visit to Belgium at the start of October.
"Whether it suits us or not, whether we like it or not, we have to work together with Turkey," Juncker said after lawmakers raised issues about the EU candidate country's rights record.
A European Commission report, held back until after the vote to avoid antagonizing Erdogan, accuses Ankara of backsliding on rule of law, freedom of expression and judicial independence, according to a draft seen by Reuters.
But should the Islamist-rooted AK Party that Erdogan founded fail again to win a majority in Sunday's vote, as most opinion polls suggest it may, the political movement and the leader who have dominated Turkey for 13 years may be forced to share power for the first time; no easy task for a man who has in the past bracketed political opposition with terrorism or treason.
A coalition with Turkey's second-largest party, the secularist CHP, could keep experienced policymakers in power while staying Erdogan's authoritarian instincts, European officials and foreign investors say.
It would also be a personal blow to Erdogan who after 11 years as prime minister won Turkey's first popular presidential poll last year, with the aim of using a strong AKP majority to bestow his largely ceremonial post with broad executive powers. Parliamentary democracy would yield to a presidential system.
"A coalition government would be good for the country," said one EU official involved in discussions. "A strong mandate for Erdogan wouldn't be so good for the EU's refugee plan. He has antagonized so many constituencies."
That has not been the message delivered to Erdogan personally, however.
Since his visit to Brussels, where Juncker presented the Turkish president with a draft joint "action plan" for cooperation on migration, a string of senior European officials have gone to Turkey in recent weeks, culminating in German Chancellor Angela Merkel's visit to Istanbul on Oct. 18.
They are looking to Erdogan to cooperate in stemming the flow of migrants and taking back those rejected by Europe, in return for money, easier travel to Europe and faster progress on Turkey's bid to join the European Union in return.
Such is the underlying resistance in many member-states to the idea of Turkish membership that few in Europe or, for that matter, in Turkey would believe entry possible, if at all, then for a decade or two. But reformers in Europe and Turkey see the negotiating process as an effective way of pressing political and economic change.
Over two million Syrians are in Turkey and EU leaders are ready to commit to 3 billion euros ($3.4 billion) in aid for Ankara via an EU trust fund, provided Ankara helps slow the migration influx that is likely to see some 800,000 people seek asylum in Germany alone this year.
Erdogan has so far showed little sign of willingness to roll over easily, accusing the EU of waking up too late to Turkey's importance and of insincerity in its membership overtures. Meanwhile, he has pressed a crackdown on opposition media and prosecutions for "insulting the President".
Opposition parties accuse Erdogan of blocking coalition talks after the last inconclusive general election in June, and his position after Sunday's vote will again be key. Many analysts suspect he is biding his time, and that even if a coalition can be agreed, it may not last for long.
But the bigger immediate question for the European Union is whether the 28-nation bloc can deliver on its promises, because its governments must sign off on any migration deal with Turkey.
Some, including Austria, Cyprus and parts of the German government, are reluctant to accelerate Turkey's EU bid.
Turkey began talks to join the EU in 2005, but a series of political obstacles, notably over Cyprus, mean much of the accession process is frozen. Merkel has offered to relaunch it, opening a new "chapter" or topic of talks as early as next year.
Yet its deteriorating security situation, battling Kurdish militants in its southeast and the spillover from Syria's civil war, has raised questions about whether it still meets the criteria even to be an EU candidate, some experts say.
"Europe has engaged in a kind of bazaar diplomacy with Turkey on the migration crisis," said Marc Pierini, a former EU ambassador to Turkey who is now at the Carnegie Europe think-tank. "But it is offering concessions without the support of all its governments, so these are almost empty promises."
(Additional reporting by Alastair Macdonald; editing by Nick Tattersall and Ralph Boulton)