With its leader Manfred Weber tipped to succeed EU chief Jean-Claude Juncker, we take a closer look at the European People's Party (EPP).
We explain what parties make-up the European Parliament's largest political grouping, what it stands for and its track record over the last five years.
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At the last European elections In 2014, EPP won 265 of the 751 seats up for grabs, helping its candidate, Juncker, become president of the European Commission.
It is hoping to win the most seats in May's election, which would put Weber in the driving seat to net the EU's top job.
Having the most seats in the European Parliament over the last five years has allowed EPP to push a centre-right agenda.
The grouping — which did well in France, Poland, Portugal and Hungary in the 2014 election but struggled in Scandinavia — tends to focus on pushing the EU's single market in order to promote jobs and economic development.
Greece's prime minister Alexis Tspiras has branded the EPP "anti-Greek" for its alleged hardline stance over the bailout.
He has called on green and left-wing factions in the European Parliament to unite and prevent so much power being concentrated in EPP hands.
The president of the European Parliament, Antonio Tajani, and the head of the European Council, Donald Tusk, are both in the EPP grouping.
EPP goes into May's election without the party of Hungary's Fidesz party after suspending it over a spat with the country's prime minister, Viktor Orban.