ISTANBUL/ANKARA (Reuters) - A fledgling Turkish political party founded by a popular former interior minister will be allowed to run in snap June elections, authorities ruled on Sunday, after 15 parliamentarians from the main opposition switched parties to bolster its ranks.

Turkey’s top electoral board ruled the nationalist Iyi (Good) Party would be allowed to participate in the polls, a board official said.

President Tayyip Erdogan this week called for snap parliamentary and presidential elections on June 24, more than a year earlier than scheduled. The announcement wrongfooted the troubled opposition and brings Erdogan closer to his long-sought goal of a presidency with sweeping executive powers.

His most credible challenge is seen coming from Meral Aksener, who last year founded the Iyi Party after splitting with the nationalist MHP, which is supporting Erdogan.

Earlier on Sunday, 15 deputies from the secularist CHP joined the Iyi Party to give it the numbers required to stand in the polls.

Parties with 20 or more deputies are recognized as groups in parliament and then automatically have the right to run candidates. The CHP has 116 members in the 550-seat parliament after the departures.The unusual move was necessary to challenge Erdogan, CHP officials said. The president is widely seen as the most popular - and divisive - politician in modern Turkish history.

“Our friends will not go down in history as MPs who left their party. They will go down as heroes who saved democracy,” CHP spokesman Bulent Tezcan told a news conference.

“This is not an easy task. It is a hard one. But these days of one-man rule are where we show our strength and ability to accomplish hard tasks.”

There has also been debate about whether the Iyi Party’s convention took place the required six months before voting day.

A masterful campaigner, Erdogan has won nearly a dozen elections and dominated Turkey since his Islamist-rooted AK party swept to power in 2002. He is admired by millions for championing the pious Muslim working classes and delivering airports, hospitals and schools during a period of strong economic growth.

His critics say his rule has grown increasingly authoritarian, pointing to the more than 160,000 people detained since a failed coup in 2016 and a widespread crackdown against the media and opposition parties.

Parliament voted this week to extend the state of emergency in place since the failed coup for another three months, meaning the June 24 vote will take place under emergency rule.