The breakup of the right-wing coalition between Democrats for Strong Bulgaria party, DSB, and the movement Blue Unity has been caused by a dispute about who would be the coalition's leader.

MEP, Nadezhda Neynski, founded Blue Unity after leaving the other right-wing party Union of Democratic Forces, UDF, in the midst of the scandal for the nomination of a constitutional judge from the parliamentary quota.

Hristo Panchugov from Neynski's movement said Tuesday they have decided to not participate in the election race, and not accept the invitation coming from DSB, led by former Prime Minister, Ivan Kostov, to join its ballots.

According to Panchugov, Kostov had caused the rift by insisting on being the only leader of the coalition in breaking the promise it will be co-chaired by him and Neynski.

Earlier in the day, speaking for bTV, the DSB election campaign manager, Veselin Metodiev, stated the party's ballots remained open for Blue Unity, adding he wished to see their candidates joining them, even as leaders of the lists.

He said the negotiations between the two formations were ongoing, something Neynski's people firmly rejected.

On Monday, DSB and the Bulgarian Democratic Forum, BDF, registered a coalition with the Central Electoral Commission, CEC. Metodiev explained then the absence of Blue Unity by technical issues such as the latter having problems to obtain bank guarantee documents on time as it has been registered only a month ago.

Hours later, Blue Unity recalled from CEC its document for participation in the snap general elections on May 12 on grounds seats in the Parliament have never been its only goal and priority.

"Our idea for coalition with DSB was to turn it to a start together on a common path to lead to a strong, united party. However, it emerged that we are the only ones to extend a hand. DSB chose division and abandoned the cause of uniting the Bulgarian right wing," an official statement of Blue Unity says.

Blue Unity is the union of politicians who left or were expelled by UDF, such as Neynski, former UDF leader, Martin Dimitrov, and former UDF MP, Vanyo Sharkov.

UDF is the party that has played a key role in Bulgaria's transition towards democracy since the fall of the Communist dictatorship in 1989.

The party has witnessed a dramatic rift recently, with the likes of Dimitrov and Sharkov being expelled over their refusal to side with the formerly ruling GERB.

The party's MPs declined to back the nomination of former President Petar Stoyanov (1997-2001) for constitutional judge, saying they did not oppose Stoyanov personally, but the fact that the nomination was imposed by now-former Prime Minister Boyko Borisov and his party GERB. They made clear their opposition to any party nomination for constitutional judge.

This forced UDF leader Emil Kabaivanov to lure three "independent" MPs loyal to GERB, to team up with the UDF leadership and table another nomination.

While UDF's leadership obviously sided with GERB, the Blue Unity declared then they were in favor of coalition with DSB and Kostov, the UDF's former partner in the so-called Blue Coalition.

Martin Dimitrov resigned as party leader after UDF voted to not have a joint ballot in 2013 with DSB as they blame Kostov for the split of the right wing in 2001.

UDF, led by Emil Kabaivanov, also registered for the election race in coalition with a number of marginal, largely unknown, parties.

Snap general elections will be held on May 12, as Borisov and his GERB Cabinet resigned on February 20.