Millions of citizens across Europe will be choosing new parliamentary representatives in Brussels this week.
However, political experts believe the vote could give more insight into national politics in each member state, rather than on the future of the EU itself.
"The European elections are a little more than a bunch of national elections," Alberto Alemanno, professor of European law at H.E.C. University in Paris, told CNBC last week.
"The European elections are a big referendum on the governing party. This is the case in France, where the French will have (for) the first time the opportunity to say what they think about (President Emmanuel) Macron," he added.
Macron was elected back in 2017 on a pro-EU platform and has framed himself as one of the core Europhile leaders in the region. However, his reform agenda, including on the labor market, has frustrated some French citizens — which has escalated into months of protests and historically-low levels of popularity for the president.
Ahead of this year's EU elections, Macron finds himself fighting the nationalist and Euroskeptic party of Marine Le Pen once again. The recently renamed National Rally (RN) party is slightly ahead in the polls, suggesting it will be a close call between the two.
"Most opinion polls suggest only around 40% of (French) voters will show up at the polling stations on 26 May. This means that Macron would have to suffer a severe defeat (by around 4-5 percentage points) for the vote to be interpreted as a rebuttal of his presidency," Teneo Intelligence, a political analysis firm, said in a note last week.
"A tie with Le Pen would probably be portrayed as a victory by Macron given his party has never competed in a European Parliament election before. It would also give the government more breathing space to push for changes to the pension system — Macron's last big reform — during the second half of the year," the same research note added.
In Italy, the elections will be a test on the anti-establishment coalition government, which has been in power for roughly a year.
Both the nationalist and anti-immigration party Lega, and the leftist Five Star Movement (M5S) are still expected to be the two biggest parties. However, there has been a shift between them. In last year's general election, M5S gathered the most votes but over time it has lost support, while its coalition partner has gathered momentum.
"The ruling (Italian) coalition … continues to effectively dominate the political debate, but competition between the two parties — widely seen as the two main rivals in any future electoral contest — has been steadily increasing," Eurasia Group, a political analysis firm, said in a note Tuesday.
"A very strong showing by the Lega (substantially above 30%), especially if combined with a weak result for M5S (approaching or below 20%), would increase the incentive for Lega leader Matteo Salvini to engineer a government collapse and early elections," the research note also said.
Other political analysts, however, are a bit more skeptical about whether Salvini will trigger snap elections this year. According to Teneo Intelligence, there has never been an election in the second half of the year since 1948. The economy is not doing very well and Salvini could give himself more time to gain further support in the south of Italy, where his party has traditionally lacked backing.
The largest economy in the EU is always a major focus in European elections. Germany is being governed by the center-right CDU party alongside the socialist SPD (Social Democratic Party of Germany) party. However, this sort of coalition has been traditionally been a challenge for the Socialists, often blamed by its voters for not standing up against Chancellor Angela Merkel's party.
The outcome of the vote could put pressure on the SPD to drop the coalition agreement and trigger a new national vote.
"The more important question will be whether the Greens can deliver on their continued lead in the polls over the center-left SPD. If this materializes, the pressure on the SPD to consider withdrawing from the coalition with Merkel will increase," Teneo Intelligence said in its research.
"The biggest implication of the European election in Germany will hence not be the distribution of seats, but its effect on government stability," it added.
There's also an important narrative to be monitored in countries like Poland, Hungary and Romania. Their governments are all at odds with the European Commission, the EU's executive arm, after it opened investigations into whether they respect the democratic values of European law.
In Hungary, Prime Minister Viktor Orban, a long-time leader with a populist and anti-immigration stance, is set to increase his share of seats at the European Parliament.
"Fidesz (Orban's party) looks stronger than ever domestically, thanks to its anti-migration campaign combined with its family support scheme. Unless there is an unexpected downside surprise for Fidesz, European Parliament elections will allow the party to expand its power. It appears poised to win 14 of Hungary's 21 seats in parliament, up from 12 currently," Eurasia said in a note.
The Hungarian prime minister has often criticized the EU and its top chiefs, including European Commission President Jean-Claude Juncker. He was one of two leaders who voted against Juncker's appointment back in 2014.
Poland is due to have a general election in November, so the EU vote will also test the ruling anti-immigration and conservative PiS party. "PiS is already feeling vulnerable," Eurasia Group said.
Until a few weeks ago, Prime Minister Theresa May was seeking to avoid holding European Parliamentary elections. The country voted to leave the EU in 2016, but that process has stalled, with the scheduled departure now expected by October 31.
By voting in the European elections, citizens in the U.K. will be able to give their assessment of how Westminster has dealt with Brexit. Eurasia Group described the vote as a "headache" for the two mainstream parties, the Conservatives and Labour. The Conservatives are polling in fifth place ahead of the vote, with a newly-formed Brexit Party in first. But low turnout and the current mood in the U.K. mean this won't necessarily translate to any national election in the future.
However, the vote is expected to impact the EU.
"The U.K.'s participation in the poll will have many adverse effects in the EU; at a minimum, it will likely aggravate tensions over who should lead the European Commission, Council and ECB and make a durable, centrist majority harder to achieve," Eurasia Group said. "If things get very messy, it could also impact the politics of a further extension of Article 50."
There are growing calls for May to leave Downing Street — a new leader could have to trigger a new election, and potentially delay the country's exit from the EU again.