Populist parties have recently chalked up wins in Italy and Austria while consolidating gains in Poland and Hungary. European Parliament elections in May may be another breakthrough and Brussels is worried.

Steve Bannon, the former far-right strategist for U.S. President Donald Trump, surprised last year when he announced plans to help populists ahead of European Parliament elections next May. Bannon presented his new initiative, The Movement, as a support network for European anti-establishment parties, and proclaimed he will spend "80 per cent" of his time on the cause.

Bannon's reception among European populists has so far been mixed. But it does point to a larger question: Will 2019 mark the next big breakthrough for the EU's populists?

This question is overshadowing elections for the European Parliament in May, as some projections foresee Eurosceptic and right-wing parties getting anywhere from 20 to 30 per cent of the vote. That kind of result could make them the strongest force in the new parliament, if they join together.

While that degree of collaboration is seen as unlikely due to divergent agendas, mainstream parties are open about their concern.

The election is about "the soul of Europe," warns Frans Timmermans, European Commission vice president and top candidate for the EU's socialists.

Far-right parties such as Germany's Alternative for Germany (AfD), Italy's League, Austria's Freedom party, and France's National Rally have all made clear they no longer want the EU in its present form. Indeed, some want no EU at all.

These politicians have also found that broadsides against Brussels resonate with many voters. Their rhetoric is laced with warnings of the "EU super state" and the "dictates of the EU."

So why do these parties wield relatively little influence in the parliament despite holding about 20 percent of its 751 seats? Internal differences are one reason. Another is that they are dispersed across three blocs.

For example, the European Conservatives and Reformists, the third-largest parliamentary faction, has many moderate eurosceptic parliamentarians and includes British Conservatives and members of Poland's Law and Justice party. It voted to expel German AfD members in 2016, who have since migrated to a more right-wing bloc.

Meanwhile, the Europe of Freedom and Direct Democracy (EFDD) group is more focused on Brexit, as it is home to the United Kingdom Independence Party. But it also includes Italy's Five Star movement, which is ideologically eclectic. Then there is the Europe of Nations and Freedom group, which includes most of the dominant far-right parties on the continent. These include Italy's League, Germany's AfD, and the other far-right nationalist parties noted above. Finally, another 23 parliaments are unaffiliated with any of these groups, but are still staunchly anti-EU.

Nicolai von Ondarza, EU expert at Germany's Institute for International and Security Affairs, points to two reasons why populist gains in 2019 may have limits.

One is that British parliamentarians who might otherwise join with eurosceptic forces will leave after their country's exit from the EU on March 29, 2019. As a result, these parties' combined total may still not exceed 20 per cent.

Another is that cross-party cooperation is "unlikely to continue in the future" due to substantive differences, notes Ondarza. This may explain why many of their leaders have been reluctant to discuss such alliances.

When it comes to populism, Italy offers an example of how populist governing can work, as two very different eurosceptic parties have formed a coalition.

Moreover, it is difficult for a populist party to offer a compelling message to a pan-European audience, says Ondarza. Nationalism can override a party's eurosceptic message, making broader coalitions difficult. These reasons can explain why Bannon has yet to breathe life into a unifying movement, and why most far-right parties have reacted coolly to his efforts.