Poland's ruling party back in the lead after Ukraine crisis

This is a significant change. For more than a year, the right-wing opposition party led by former prime minister Jaroslaw Kaczynski was 5-7 percentage points ahead of the ruling party.

Until this spring, voters were turning away from Donald Tusk's party due to growing dissatisfaction with his government, which has been in power for over six years.

Last year was not a good year for the Polish economy and unemployment increased to more than 14 percent.

However, the Ukrainian crisis and the government's strong response has changed the trend in the polls. In Poland, the PO succeeded in moving the campaign from domestic issues to foreign policy, where it feels stronger.

As tensions rose in February, Donald Tusk toured Europe and met 11 leaders of EU member states. The Polish foreign minister, together with his German and French counterparts, played a key role in resolving the crisis in Kiev.

Tusk was also very active at the European summit, when EU leaders were deciding on Europe's response to Russia's annexation of Crimea.

"This won't be elections about the banking union or who gets more money in the EU," Tusk said at the party convention on 22 April. "It is about the core of our European history; we will decide whether Europe will survive." One of the guests at the convention was Ukrainian boxer and political leader Vitali Klitschko.

PiS is trying to steer the campaign back to domestic politics, but without success.

Jaroslaw Kaczynski wanted to hold a debate with Tusk and experts on the health service, but the PM turned his offer down.

The opposition accuses Tusk of frightening voters with the threat of war. In one of his speeches, the PM said that we do not know whether "children will go to school this autumn".

"No one went that far in scaring Poles," said Leszek Miller, the leader of the left-wing SLD, which is third in the polls with 10 percent support.

"But Europe's real problems are somewhere else. They are high unemployment, the lack of perspectives for young people, growing poverty and rising euroscepticism," he added.

But while recent polls show that PO is back in the game, it does not mean that the ruling party will definitely win.

The campaign will be hard fought, as the margin in the polls between the main competitors, PiS and PO, is still very small.