The parties of leaders like French President Francois Hollande and British Prime Minister David Cameron were shaken to the core by anti-EU challengers, yet they have offered starkly different alternatives on how to deal with the situation ahead of today's EU summit.
Hollande has said that "France's future is in Europe" and has remained steadfast in the defence of joint policies and common stands on major issues.
The first battle will likely be over Jean-Claude Juncker, the former prime minister of Luxembourg and longtime leader of the group of nations with the euro currency, who wants to replace Jose Manuel Barroso as leader of the EU Commission.
The post is important since the commission proposes legislation and runs much of the day-to-day affairs of the EU.
Also Read
Juncker is seen as a master dealmaker in backrooms and a committed federalist which is anathema to the Brits.
In case he gets enough parliamentarians to support him, he will still have to convince the overwhelming majority of government leaders. The whole process could take several weeks.
For Nigel Farage, the leader of the UK Independence Party which overtook Cameron's Conservatives in the EU elections, choosing Juncker was yet more proof the parliament was tone deaf to change.
"You know, there is a big dissident voice now in this parliament. And yet, I just sat in a meeting, where you wouldn't have thought anything had happened at all, and it was business-as-usual," Farage said after the conference of party leaders.
He was challenged for the job at a meeting ahead of the summit by Martin Schulz, president of the S&D Socialist of European Parliament group and Guy Verhofstadt of the liberal ALDE group.