The sound of gunfire rang out on the streets of Paris again last week. On Thursday Karim Cheurfi, drove his car along the city’s famous Champs-Elysee boulevard, stopped and got out, before firing a Kalashnikov assault rifle killing police officer Xavier Jugele, with two bullets to the head.

It was the one thing everyone feared would happen. The latest in a series of terror attacks by Islamist extremists that have shaken France and brought another twist to an increasingly unpredictable presidential election race.

Today that race reaches a crucial juncture as the country goes to the polls in the first round of voting in France’s two-stage election, one of the most closely watched and anticipated in many years.

Currently there are 11 candidates in the running to become the country’s next president, but only five are considered serious contenders: far right National Front (FN) leader Marine Le Pen, centrist Emmanuel Macron, former prime minister Francois Fillon, socialist Benoit Hamon, and Jean-Luc Melenchon on the far left.

For all these candidates Thursday’s attack could not have come as much of a surprise.

“It was clear that the self-proclaimed ‘Islamic State’ would try to destabilise the country during the election,” said Sebastian Roche, a security expert at the Sciences Po Institute of Political Studies at the University of Grenoble, speaking to German broadcaster Deutsche Welle. “Authorities were counting on it.”

Just around the time Cheurfi was firing his rifle in the heart of Paris, all 11 candidates were in the middle of their last televised debate. When news of the attack reached the France 2 television studios, all the politicians initially focussed their attention in expressing their condolences to police.

“Don’t panic. We must not interrupt our democratic process. It is our responsibility to avoid polemic bickering,” insisted leftist candidate Jean-Luc Melenchon, the master of the acid one-liner. He would later win plaudits in the debate after accusing the moderators of having the “modesty of a gazelle” for failing to grill Fillon and Le Pen over their legal woes that include the abuse of public funds.

But Melenchon’s wider appeal to avoid bickering was to fall on deaf ears, and it didn’t take long before electioneering mode took over.

Suddenly security and terrorism concerns were once again thrust to the forefront by all the key contenders for maximum political effect in the final hours of campaigning.

With their radically opposing visions for the country’s future, all clashed openly over the response to the killing,

Republican Francois Fillon once again called for more drastic measures to deal with “known threats” and “radical preachers.”

Far right candidate Marine Le Pen of the National Front meanwhile, repeated her well-known mantra that France must withdraw from the Schengen Area, close its borders and stop “uncontrolled immigration.”

The frontrunner, independent centrist candidate, Emmanuel Macron, simply accused his two closest rivals of using the killing of the policeman, and the serious wounding of two other officers, to score political points.

Macron suggested Le Pen, with whom he is neck-and-neck in polling for the first-round vote, and Fillon - currently in third place - were engaging in one-upmanship in their response to the attack.

But the reality was that all were to some extent guilty of using the attack for electioneering leverage.

“We must not give way to panic, nor in any way allow any attempt to manipulate these events,” Macron said at a press conference. “The terrorists want to destabilise the country … at a time when the French are deciding on their future,” the former investment banker and economy minister insisted.

Wading into the fray from outside France, US President Donald Trump added to the political acrimony in the only way he knows how: Twitter.

“Another terrorist attacks in Paris. The people of France will not take much more of this. Will have a big effect on presidential election!” Trump, wrote on social media contributing what some observers pointed out was a bit of electioneering of this own.

While stopping short of endorsing her explicitly, Trump has lavished praise on Le Pen, saying Thursday’s attack would help her because she’s the candidate who is “strongest on borders, and she’s the strongest on what’s been going on in France.”

But the notion that the attack could effectively hand the election to Le Pen, who has taken a hardline stance on terrorism, is misplaced, according to Dr Emmanuelle Schon-Quinlivan, lecturer in European politics at University College, Cork.

“If this had been the first attack, it might have had an impact,” she said. “But we’ve had so many attacks and we’re too close to election now.”

Her views are shared by another French political expert Bruno Cautres from the Cevipof think-tank, who also believes the impact on voters of the latest terror attack will be minimal.

“I don’t think it will change much at this late stage,” insists Cautres. “The campaign has been running for months now and most voters know the candidates they will vote for.”

For some time now France’s presidential election has been framed as a referendum on globalisation, immigration and France’s place in the world. Marine Le Pen would certainly like it to be seen that way.

Just as Donald Trump did in his own presidential campaign, election watchers say Le Pen thrives on an intensely gloomy view of her country’s present condition.

While most election analysts agree that globalisation, immigration, and France’s status are all key issues, jobs they say, continue to be the most significant of all issues to voters. This has been borne out over many months now by the results of numerous polls.

Currently the French unemployment rate stands at around 10 per cent. This is higher than the Eurozone average of 9.5 per cent and more than double the rates in the UK and Germany.

Youth unemployment is even higher at around 25 per cent, due in part to the country's rigid labour market and a tax system that makes it expensive for employers to hire or fire full-time employees. This lack of economic prospects will be a decisive factor in a presidential race predicting the outcome of which continues to prove difficult.

The first poll conducted entirely after Thursday's attack suggested Le Pen had gained some ground on Macron. While Macron was still seen as winning the first round with 24.5 per cent, his score slipped half a percentage point while Le Pen's rose by one to 23 per cent.

Conservative Francois Fillon, and the far left’s Jean-Luc Melenchon meanwhile were both down half a percentage point on 19 per cent in the Odoxa poll for the newspaper Le Point.

All 11 candidates will be on the ballot paper for the first round, and assuming nobody claims more than 50 per cent of the vote - something that has never happened - the most popular two will move forward to the second and final round on May 7.

Polling stations opened this morning at 8am and in larger cities like Paris will stay open till 8pm for both rounds of voting. After Thursday’s attack an emergency meeting of security officials was quickly convened, and Prime Minister Bernard Cazeneuve said security forces, including elite units, were on alert to back up the 50,000 police earmarked to ensure safety during today’s poll.

Those closely following the election say there are three things to look out for over and above security concerns. The first is voter turnout, the second who makes the next round with what, and the third whether those undecided finally decide which way they will cast their vote.

Opinion polls are indicating that more than a third of the country’s 45.7 million voters might abstain in the first round of voting.

According to a recent Reuters poll, around one third of those intending to vote are still undecided with reasons ranging from political apathy, dislike of certain politicians and disgust over the clutch of scandals that have dogged the campaigns of various candidates.

A low turnout will probably benefit Le Pen and Fillon, as their voters are more likely to turn out for them than Macron or Melenchon’s supporters, according to Martin Michelot deputy director of the think-tank Europeum Institute for European Policy

Analysts point to the fact that this would not be unlike the Brexit referendum that sneaked through in part thanks to a dismal turnout in key parts of London.

Then there is the question of which two candidates will make it through to the second round and by what margin.

Right now, the four leading candidates, Fillon, Le Pen, Macron and Melenchon, are near neck and neck. If the first and second place holders emerge a healthy distance ahead of the runners up, a contentious, clear-cut competition can be expected to take place in the two weeks that follow.

But if the third and fourth place finishers come in close, then their voters will have a major role to play in the run-off, perhaps as spoilers.

“Never before have so many voters remained undecided so close to election day, many will be making choices based on a strategic calculus rather than an assertion of preference,” observed James Traub contributing editor at Foreign Policy magazine and fellow at the Centre on International Cooperation.

“That calculus is: How can I prevent Marine Le Pen from becoming president of France? ”

Traub points out that recent revelations that Le Pen’s closest advisers are Nazi sympathisers have only further ratcheted up fears of a National Front victory. Voters on the left he says are “racking their brains over the ideal strategy to keep that from happening.”

The most likely beneficiary of this so-called ‘vote utile’ or tactical voting is Macron, whom moderate leftists and moderate conservatives both feel they can live with.

All this suggests that this topsy-turvy race might yet have a few more surprises left. And this too before factoring in the impact the election result might have on the EU.

Most worrying for the EU is of course the prospect of Paris turning its back. European diplomatic and politics analysts remain convinced the bloc would not survive Frexit.

In Brussels then they will be hoping that a victory for overtly pro-EU centrist Macron would offer France a chance to reform, and Europe a chance to rebound.

“It would show that liberal, pro-EU centrists may yet have a future in European politics,” says Charles Grant of the Centre for European Reform.

“Macron wants reforms to pep up France’s economy and strengthen its position in Europe.”

A Macron win could also suggest that, after Britain’s decision to leave and the shock election of Donald Trump in the US, the demise of liberalism, internationalism and the EU may not be inevitable, Grant observed.

Markets for now remain uncertain and investors jittery given the popularity of anti-European Union candidate Le Pen and Eurosceptic Jean-Luc Melenchon.

But speculation on the future of the EU is of course just that, speculation, as the first round of the French election is only just underway.

By later this evening the big French TV networks will be free of the blackout rule that effects elections in the country. From around 8.30pm, results will start to be declared from all over France as local authorities send their data to the interior ministry.

For those looking for early signs of how candidates faired, campaign staffers say that Angers, the western city of 150,000 people is considered a good representative sample of French voters sociologically. Others mention the Bouches-du-Rhones departement, which includes Marseille and its outskirts, as it has conservative, far right, far left and socialist strongholds.

As the results become clear those two candidates who have made it through to the second round will be declared. For those knocked out they will immediately be under pressure to tell their supporters whom to back in the run-off. It will be a fascinating battle and one that has some way to go yet. France, Europe and the world watches and waits.