Turkey's secular opposition leader may have succeeded in forcing President Recep Tayyip Erdogan into his first ever runoff, but his chances of winning on May 28 are remote.

Kemal Kilicdaroglu was predicted to perform well in Sunday's first round but ended up with just under 45 percent while Erdogan fell fractionally short of the 50-percent threshold required for an outright victory.

His six-party alliance now needs to accomplish seemingly impossible electoral gymnastics to unseat Erdogan, who needs just a sliver of extra support to extend his two decades in power to 2028.

"The second round will be easier for us," Erdogan spokesman Ibrahim Kalin said on Tuesday. "There is a difference of five points, close to 2.5 million votes. It seems there is no possibility of this closing."

Mobilising more young voters could boost Kilicdaroglu's prospects, with polls suggesting he will win that group by a two-to-one margin.

More than five million first-time voters -- who grew up knowing no leader other than Erdogan -- were eligible to vote on Sunday and are deemed more likely to want change.

Kilicdaroglu, a 74-year-old former civil servant, tried to revive his campaign on Tuesday with a message targeted at young people.

"You can't afford anything. You even have to think about a cup of coffee. Your joy of life has stolen, whereas youth is carefree," he said on Twitter.

"They didn't give you that even for a day."

- Kurds: a double-edged sword? -

Kurds, a minority ethnic group representing around 10 percent of the electorate, may also come out stronger in favour of Kilicdaroglu.

The opposition leader, himself an Alevi Kurd who represents one of Turkey's most repressed communities, was endorsed by the pro-Kurdish HDP party in late April.

But Sunday's turnout in Kurdish-majority provinces was believed to hover around 80 percent -- well below the national average of almost 89 percent.

Greater Kurdish support may also be a double-edged sword that makes Kilicdaroglu's bid for power near impossible.

One of Erdogan's attack lines was linking the opposition to outlawed Kurdish militants that have waged a deadly insurgency against the Turkish state for decades -- an appeal to nationalist and conservative Turks that appeared to work.

"On balance, Kilicdaroglu's electoral alliance with pro-Kurdish HDP hurt him," said Washington Institute analyst Soner Cagaptay.

"Some HDP voters in Kurdish-majority provinces stayed home on election day, while some Turkish nationalist voters abandoned Kilicdaroglu, admonishing him for allying with the HDP."

Sinan Ogan, a nationalist third candidate, picked up five percent of the vote and his support could be crucial in the second round.

He is a secular nationalist, which separates him from religious conservatives who have rallied around Erdogan.

But he has also campaigned strongly against "terrorism", a word that many Turkish politicians use to condemn Kurds.

- Easier time for Erdogan -

"Anti-Kurdish nationalism of this line represented by Ogan... makes it very difficult for Kilicdaroglu to strike a deal," Kursad Ertugrul of Ankara's Middle East Technical University told AFP.

Even if Kilicdaroglu somehow earned Ogan's backing, that would probably alienate the Kurdish vote, said Berk Esen, a political science professor at Sabanci University in Istanbul.

The disparate six-party opposition alliance, which only selected Kilicdaroglu as their joint candidate after a year of bitter argument, now also faces the challenge of staying united after Sunday's disappointment.

"Erdogan will have an easier time than Kilicdaroglu wooing voters," especially Ogan's backers, noted Emre Peker of the Eurasia Group consultancy.

"The president's supporters are also likely to turn out in greater numbers to vote in the runoff than Kilicdaroglu backers as opposition... momentum ebbs."

Having won 49.5 percent in the first round, Erdogan does not need to make major concessions to Ogan to win on May 28, added Esen.

Erdogan's campaign is likely to stay focused on security issues, a winning formula among Turkey's "conservative-nationalist" working class despite the severe impact of the economic crisis, Ertugrul told AFP.

The idea of a "great Turkey" being forged through infrastructure projects and tapping into "the conservative sensibilities of the 'moral majority'" were also at the heart of Erdogan's messaging, he added.

"This campaign (irrespective of the truth of the statements) seems to have resonated with his social base."