Czech voters were headed for the polls on Friday as European Parliament elections reached the east, where the Ukraine crisis is expected to hurt eurosceptics, while Ireland also joined the four-day ballot.
Russia's annexation of Crimea has spooked many eastern European countries that were dominated by the Soviet Union for much of the 20th century.
Having anchored their security in the EU and NATO following the fall of the Iron Curtain, most of eastern Europe is expected to back pro-EU parties in the European Parliament polls.
"The crisis in Ukraine may... push some voters to back mainstream parties and eschew those of a eurosceptic bent," Vit Benes, from the Prague-based Institute of International Relations, told AFP.
Helping to push that trend is the fact that "eurosceptic parties like the National Front in France or Britain's UKIP are pro-Putin," he said, referring to Russia's president.
Ireland and the Czech Republic were voting in the second day of polls on Friday. Latvia, Malta and Slovakia hold their polls on Saturday, while the rest will vote on Sunday.
In the Czech Republic, which had previously eyed EU controls with unease, two governing pro-EU parties are set to top the polls, with the populist ANO party poised for victory ahead of the leftwing Social Democrats.
Ireland also began voting for the European Parliament on Friday. Anger over EU-imposed fiscal policies was expected to see a boost for anti-austerity candidates from Sinn Fein.
But despite a string of domestic controversies since its international bailout ended in December, the ruling Fine Gael party was still expected to return two, or possibly three, MEPs out of the 11 up for grabs.
- Dutch populists 'disappointed' -
The Czech and Irish vote comes a day after Dutch voters dealt a surprise blow to eurosceptic and fiercely anti-Islamic populist Geert Wilders, whose Party for Freedom won just 12.2 percent of the vote, down from 17 percent at the last election in 2009, according to an IPSOS exit poll.
The polls showed the pro-Europe centrist D66 and CDA Christian Democrats winning the most votes, with 15.6 percent and 15.2 percent respectively.
A rally of Wilders' party faithful at a beachfront pub in The Hague fell silent as the predictions were released.
"The exit polls are disappointing," Wilders said, blaming the result on the low turnout of 37 percent.
However, Britain's UK Independence Party (UKIP) led by Nigel Farage, was expected to score big successes after that country's vote on Thursday, although results will be announced Sunday night.
Some 400 million Europeans are eligible for the elections, spread over four days in the EU's 28 member states, and which come as the EU struggles for relevance in the aftermath of the eurozone crisis and grapples with the chaos on its eastern borders.
With 26 million people out of work across the EU, eurosceptic and far-right parties have picked up massive support on anti-immigration and anti-EU platforms.
The latest opinion polls showed eurosceptics could secure almost 100 seats in the new parliament, trebling their number in the 751-seat assembly, and may top the polls in Britain, France and Italy.
But in the east of the continent, only Hungary, which votes on Sunday, has a strong eurosceptic party -- the far-right Jobbik.
Dubbed "neo-Nazi" by the European Jewish Congress and shunned even by France's far-right National Front and Austria's Freedom party for its extremism, Jobbik has emerged as the second strongest political movement in Hungary, with polls showing support of around 17 percent.
Regional heavyweight Poland is among the most enthusiastic EU supporters. A recent Pew Research Centre poll showed 72 percent favoured the EU.
Europhilia is particularly pronounced in the Baltic states, which were annexed by the Soviet Union after World War II, and now fear a resurgent Russia.
- Political 'earthquake' -
But in Britain, UKIP's rise has rocked the political establishment as a party without a single seat in its national parliament heads into the European election ahead of the main opposition Labour Party, according to opinion polls.
The party's rise was seen as a factor in Conservative Prime Minister David Cameron's pledge to hold a referendum on Britain's membership of the EU in late 2017.
Farage has ruled out joining a far-right bloc of Wilders' party and France's National Front, led by Marine Le Pen, saying the National Front is anti-Semitic.
As he cast his vote in a village school, Farage rejected claims his party was racist and said he wanted to cause a political "earthquake".
"If we get what we like, things will never be quite the same again," he told reporters, with his party expected looking certain to increase the nine seats it currently holds.
Former French president Nicolas Sarkozy reignited the debate on the other side of the English Channel, saying that reform of the EU was necessary to halt the rise of populist parties.
In an opinion piece published Thursday, Sarkozy called for the end of Europe's visa-free Schengen area and the creation of a Franco-German economic bloc at the heart of the eurozone.