ANKARA (Reuters) - A small Turkish Islamist party is targeting religious voters it says are disenchanted by the authoritarian rule of President Tayyip Erdogan, aiming to erode his support in what may turn into a closely-fought parliamentary vote.

Turkish President Tayyip Erdogan delivers a speech at a meeting to present his ruling AK Party's lawmaker candidates for the city of Istanbul, Turkey, May 29, 2018. REUTERS/Osman Orsal

The Saadet (Felicity) Party has never won more than 2.5 percent of the vote in parliamentary elections, but its alliance with secularist and nationalist opposition groups has boosted its chances of winning seats for the first time on June 24.

With polls showing Erdogan’s ruling AK Party and its nationalist partner gaining around 50 percent support, marginal swings either way could prove crucial to his hopes of a majority in the legislative assembly.

Turkey’s most successful modern politician, Erdogan remains strong favourite to win re-election the same day to a newly empowered executive presidency. But losing control of parliament could offset some of the sweeping powers he has fought to win.

A strong showing by the Felicity Party, which shares the same Islamist roots as the AK Party, could also help the opposition attract enough voters away to force the presidential vote into a second round, when the opposition alliance has agreed to unite around a single candidate.

Felicity Party leader Temel Karamollaoglu said Erdogan’s party had strayed from its founding principles, and said his group was ready to capitalise on disillusioned AK Party supporters.

“We now think that around 15 percent of voters are unhappy with the government’s actions and are in search (of another party). I believe the majority will lean towards us,” he told Reuters in an interview.

During the 1990s Karamollaoglu and Erdogan were comrades in the Welfare Party, which formed Turkey’s first Islamist government but was toppled in 1997 and later banned. Erdogan’s political breakthrough came when he was in the Welfare Party ranks, as he won Istanbul mayor elections in 1994.

The softly spoken, 77-year-old Karamollaoglu, who is also running for president, criticised the rhetoric used by Erdogan and his main challengers, saying that in Erdogan’s case it had lost its appeal.

“The rhetoric and speeches of the president don’t have the same reaction in the public anymore, people are tired,” he said.

“CHIEF KNOWS BEST”

A survey by pollsters MAK, viewed as sympathetic to the ruling party, showed last week that the parliamentary race is too close to call, with the AK Party together with its nationalist allies winning exactly 50.0 percent.

In the presidential vote, it put Erdogan at 51.4 percent. Support for Karamollaoglu as presidential candidate is somewhere between 2 and 3.5 percent, according to polls.

Felicity has never won the 10 percent support required to enter the legislative assembly, but its alliance this year with several opposition parties will help it to exceed the threshold.

Karamollaoglu predicted far higher support for his party than polls were suggesting, saying surveys were unreliable because people were afraid to speak their mind.

After 15 years in power, the AK Party had become a platform for one-man rule, he said. “‘The chief knows best’. That’s what they say and that’s it,” he said.

Concern that Turkey’s justice system has been weakened under Erdogan was also turning supporters away, Karamollaoglu said.

“The disappearance of justice is already worrying everyone, people are concerned about openly voicing their opinions,” Karamollaoglu said.

Authorities have detained 160,000 people and dismissed nearly the same number of civil servants since a failed military coup nearly two years ago, the U.N. human rights office said in March. Of that number, more than 50,000 have been formally charged and kept in jail during their trials.

The government says the measures are necessary to combat threats to national security, but they have alarmed rights groups and Turkey’s Western allies, who accuse Erdogan of using the failed putsch as a pretext to quash dissent.