Graham Stack in Kyiv -

Ukraine's two main opposition parties have signed an electoral pact agreeing to run a joint list of candidates going into parliamentary elections in October 2012. The question now is whether they will be able to get more opposition parties to join them.

The move to unite by Batkyvschina and Front Zmin could pose a real challenge to the ruling Party of Regions of President Viktor Yanukovych. A recent opinion poll conducted by Razumkov Center give Batkvyschina 14% and Front Zmin 10% of voters' preferences. The survey gave the Party of Regions 19% support, a sharp drop from the honeymoon it enjoyed following its election in 2010, when it saw approval at around 40%.

The election campaign will kick off at the end of July, and Arsenyi Yatsenyuk, leader of Front Zmin, said jailed former Prime Minister Yulia Tymoshenko, who leads the Batkyvhsina party, will head the pair's joint electoral list. However, with Tymoshenko barred from running due to her recent conviction for abuse of office, it's expected that Yatsenyuk will in reality take the number one spot and cement the alliance.

At just 37, Yatsenuk is a rarity in Ukrainian politics, being young, plausible, and relatively unbesmirched. However, he also packs a punch in terms of experience, having had stints as head of the national bank, parliamentary speaker and foreign minister, as well as taking 7% of the vote in the presidential elections in January 2010. He has a better track record of building and sustaining alliances, say analysts, and is less associated in voters' minds with the disappointment following the Orange Revolution in 2004.

Before her jailing in October, Tymoshenko's team were rubbishing Yatsenyuk behind the scenes as being part of the "loyal opposition" receiving favours from Party of Regions. However, Tymoshenko's is ego no longer in the way of a union of opposition forces, which has looked unlikely until now. At the same, the former PM plays an important role behind bars as a potent symbol of political repression.

The united opposition will still have an uphill battle due to changes to electoral legislation made by the Party of Regions. These include a shift back to using first-past-the-post constituencies to elect half of the Rada's deputies. This is seen to be advantageous for the Party of Regions due to its domination at local level across wide swathes of densely populated East Ukraine.

"The PoR seems capable of securing a majority in the next legislature by offsetting its potential underperformance in the proportional representation segment of the ballot by a stronger showing in single-seat constituencies," write Dragon Capital analysts. "We think this alliance is unlikely to present a major challenge to the PoR as long as other opposition parties ... decide to run separately and nominate their own candidates for single-seat districts."

Thus it is crucial for the new alliance to reach out to other opposition parties, most importantly popular boxing champion Vitaly Klitschko's UDAR party, which takes around 7.4% of voters' preferences in opinion polls currently. Klitscho would require the alliance's support of his candidacy for the position of mayor of Kyiv in exchange. The election date for the post of mayor has not yet been fixed.

"An alliance between the pro-democracy opposition forces has been widely anticipated," points out Concorde Capital's Brad Wells, "but after years of failing to agree to almost any major joint initiatives - this is a positive development."