With Cyprus's ruling DISY out of the presidential race for the first time in its history, the conservative party's decision to back neither candidate has thrown Sunday's run-off wide open.
Last Sunday's first round results and the DISY development have changed everything.
"I expect a close result, and either of the candidates can win," said Hubert Faustmann, a politics and history professor at the University of Nicosia.
"The choices of the DISY supporters will decide this election."
Cypriots in the divided island's south vote again Sunday, with both candidates trying to prove their credentials to govern independently of the parties that back them.
Former foreign minister Nikos Christodoulides faces career diplomat Andreas Mavroyiannis in the second round after neither secured a majority last weekend.
The winner succeeds two-term President Nicos Anastasiades as the republic's eighth president.
Pre-poll favourite Christodoulides led a close-fought contest with 32.04 percent of the vote, followed by Mavroyiannis with 29.59 percent.
He unexpectedly squeezed out Averof Neofytou, leader of the island's largest party DISY, who came third with 26.11 percent.
Despite Anastasiades' endorsement, Neofytou is the first DISY candidate in the party's history not to progress from the first round.
- DISY now in opposition -
Mavroyiannis, a 66-year-old technocrat backed by the communist party AKEL, surprised observers by pipping Neofytou, 61, and closing the gap with the 49-year-old centrist-backed Christodoulides.
"The dynamics are currently favouring Mavroyiannis because the anger in DISY over the result seems to be bigger than their dislike for AKEL," said Faustmann.
"The elections will be decided by the bulk of DISY voters who must choose between the candidate of their political and ideological archrival AKEL and the defector responsible for their worst result in modern history."
This week, DISY decided not to endorse either candidate but to declare itself an opposition party.
Neofytou felt betrayed by Christodoulides, a senior DISY member who broke ranks to declare his candidacy instead of toeing the party line.
Trying to mend fences, Christodoulides offered a "significant role" for DISY in his government if elected.
But Neofytou told the party faithful: "History might forget heroes, but it never forgets traitors."
Every vote counts, and extreme right-wing party Elam could be key -- its party leader Christos Christou came fourth last week on six percent.
"Their voters are very likely to support Christodoulides, but what will Christodoulides offer them in return?" Faustmann said of Elam.
"A position in the cabinet would probably cost him more votes than he would gain," he added, also acknowledging that other parties backing Christodoulides reject Elam.
- Rooting out corruption -
Mavroyiannis could upset the odds, but he must convince voters that AKEL will not control economic policy.
The communists are widely blamed for the 2013 financial crisis which almost bankrupted the eurozone country before a bailout from international lenders.
"There is overwhelming consensus from that experience that AKEL should not have its hand on economic policies," Faustmann said.
Mavroyiannis took the unusual step on Wednesday of naming his future finance minister if elected, respected lawyer Charalambos Prountzos, an expert in corporate and energy law.
Rooting out corruption and improving the economy -- rather than focusing on the island's division -- have been major issues for the 561,000 registered voters.
The new government will be under pressure to address higher energy prices, labour disputes and a struggling economy amid a global recession.
Cyprus has been divided since 1974 when Turkish forces occupied its northern third in response to a Greek-sponsored coup.
Peace talks with the self-proclaimed Turkish Republic of Northern Cyprus, frozen for nearly six years, will also be on the new president's agenda.