The terrorist attacks in Paris have come at a supremely sensitive time in French politics, just three weeks before regional elections in which the far right is tipped to make historic gains.

It may be “just a local vote”, political analyst Madani Cheurfa told the Observer, “but everything depends on how the Front National reacts and if Marine Le Pen manages to get the FN to speak with one voice.”

Will Le Pen, head of the FN, be forced to echo the rivals she detests to show a united front against terrorism, as she did after the Charlie Hebdo killings in January? Or will she play the race and religion card?

Political observers suggested the answer would come only after the country had grieved for and buried its dead, but added that Friday night’s events were likely to play into the hands of the far right.

“The difference between this and Charlie Hebdo is that then it was journalists and police, symbols and institutions of the republic. These latest attacks were against ordinary people, all and everyone, men, women, children,” said Cheurfa, an analyst with Science Po’s research thinktank Cevipov.

“And they allow the FN and Marine Le Pen to say, ‘I told you so, we’ve been talking about this threat for years but nobody listened, so give us your vote.’”

Le Pen was already prosecuting some anti-Europe, anti-Islam themes during a brief conference at the FN’s headquarters on Saturday, hours after the attacks that left at least 128 dead and hundreds injured.

“We are living the horror … yesterday evening the centre of France was struck by an exceptional barbarity. It was an escalation of Islamist terrorism and the sixth time this year that Islamists have attacked our country,” she said.

Le Pen said it was vital that France clawed back control of its borders “for good”, in defiance of the European Union, and called for a crackdown on “hate preachers” and extremists. “Islamic extremism must be crushed,” she said.

Opinion polls in recent elections have been deeply misleading, suggesting the FN, while rising in popularity, would do much better than it did. At the departmental elections in March, numerous surveys suggested councils were about to be taken over by the FN. While more FN candidates were indeed elected, the far right did not gain enough support to run any department.

However, the FN is hopeful that its two leading female figures, Le Pen in the Nord-Pas-de-Calais-Picardie region and her niece Marion Maréchal Le Pen in the Provence-Alpes-Côte d’Azur, will do the party proud this time around, and all indications suggest that might be the case.

With one eye on the presidential election in 2017, still some way off, but getting closer, the departmental elections are seen as a last chance at electoral jostling for positions in the run-up to the main event.

The FN rhetoric feeds into the national sense of being under threat, which was sparked by the January attacks on Charlie Hebdo, the ongoing European refugee and migrant crisis, and now Friday’s terror attacks.

“What unites us is an unconditional love for France,” Maréchal-Le Pen said at a recent campaign meeting in the French Riviera, suggesting that this was something unique to the FN and marked it out from the ruling Socialist party or opposition group Les Républicains.

On SaturdayYesterday, there was a rare agreement across the French political spectrum as all parties, including the FN, agreed to suspend their election campaigns.

“The war is now among us. We will resist, we will fight together,” wrote former centre right prime minister François Fillon on Twitter. Fillon saluted President François Hollande for “taking the necessary decisions for the security of the French … national unity is now our duty.”

Former president Nicolas Sarkozy also supported Hollande’s decision to declare a state of emergency.

“In such tragic circumstances, all French have to show solidarity against terrorists who have declared war on France.”

Leading FN figures, however, broke ranks with the declarations of national unity.

Louis Aliot, candidate for the FN in the Languedoc-Roussillon-Midi-Pyrénées and Marine Le Pen’s partner, said: “Mr Valls, you see where the danger lies? The real danger!”

Gilbert Collard, a lawyer and leading member of the FN, wrote on his website: “National identity … Marine and our people, in power quick.” He added: “Those habitual defenders of great principles, those who defend Islam and its principles, they are the ones who should be in prison. Quickly. It’s now a question of our survival.”

Le Pen is due to meet Hollande at the Elysée on Sunday. Hollande enjoyed a brief respite from record unpopularity for what was seen as his statesmanlike response to the attacks in Paris in January, at Charlie Hebdo and a kosher supermarket, which left 17 dead.

However, any plaudits he may receive from his reaction to the latest attacks are thought unlikely to convert into votes for the Socialist party, trailing third in the polls.

“This could play well for the FN and Marine Le Pen,” Laurent Bouvet, author and professor of political science at the University of Versailles, said.

“In the aftermath of events like this there is always a sense of national unity, but as we saw after Charlie Hebdo, it tends not to last very long and the debate becomes political again quite quickly.

“Usually, events like Friday night tend to back up the line taken by Marine Le Pen and the hard right. In this case, there will be questions about whether the government did everything necessary after Charlie Hebdo and whether the latest attacks could have been prevented.

“All this plays into the hands of a Front National that was already riding a positive dynamic even before the attacks.”

Bouvet, whose book L’Insécurité Culturelle, published in March, examines why France’s working class is abandoning the left and ready to vote FN, added: “At the moment, we are too close to the events, but I would imagine the FN will benefit electorally from this.”