A Le Monde editorial this morning said the attack might benefit far-right candidate Marine Le Pen, who has made the threat of Islamist extremism and immigration her main talking points. FN vice-president Florian Philippot responded to Cazeneuve on Twitter, saying the prime minister should "have resigned a long time ago for his incoherence and lack of rigour".
However previous attacks that have taken place soon before elections, including the November 2015 attacks in Paris ahead of regional polls and the shooting in a Jewish school before the 2012 presidentials, did not appear to change the course of those ballots in favour of those espousing tougher national security.
Friday is the last day of campaigning before Sunday's election.
Scandal-hit conservative François Fillon and Communist-backed Jean-Luc Melenchon were both slightly down, to 19pc, which would eliminate them from the May 7 run-off.
Thursday's attack, which was claimed by Islamic State, was carried out by a man who got out of a auto that pulled up next to a police van on the Champs Elysees and opened fire on officers inside and outside the vehicle.
On its media channel, Amaq, ISIS claimed that the attack was carried out by "Abu Yousuf al-Baljiki (the Belgian) and he is one of the Islamic State's fighters".
The attack occurred during the final televised debate of the campaign, and Ms Le Pen told viewers that France needed a new plan to deal with terrorism "with new measures and with borders".
France's anti-terrorism prosecutor said Friday the gunman had a note with him defending the Islamic State group.
One policeman was shot dead and two others were wounded in Thursday night's attack. But his health care bill didn't come up for a vote in the House, his travel ban was twice blocked in the courts and his West Wing has been plagued by infighting and the resignation of his first national security adviser amid an ongoing investigation into contacts between Trump aides and Russian officials.
Terrorist attacks have become a fact of life for many European countries.
"We can not afford to lose this war".
Le Pen visited Trump Tower in January although she did not meet with the then-president-elect.
If Melenchon makes it to the runoff, he was projected by the survey to beat either Le Pen or Fillon by comfortable margins, although he was seen losing to Macron by 41% to 59.
Le Pen, widely seen as taking the hardest line on security, has called for France to "immediately" take back control of its own borders from the European Union and deport all foreigners on a terror watchlist.