An Elabe survey of voter intentions taken before the shooting on the Champs Elysees shopping street in central Paris showed Macron in front and far right leader Marine Le Pen falling further behind him.
But even leaving out the potential impact on voter sentiment of the latest deadly attack in a series that has hit France in the past two years, neither was totally assured a spot in the May 7 runoff round.
Two other candidates were snapping at their heels.
The poll was conducted on Wednesday and Thursday - before the shootout in which the attacker also died and two other police officers were injured.
The attack was swiftly claimed by terrorist Islamist group ISIS.
Le Pen has made immigration and security a core part of her campaign.
She wants to tighten French borders controls and build more jails, and says authorities are not doing enough to protect citizens from attacks like Thursday's. Such attacks have claimed more than 230 victims in France since January 2015.
"Today fundamentalist Islam is waging war and... the measures are not being taken to limit the risks," she said on RFI radio.
Macron, who from 2014 to 2016 was economy minister in the Socialist government she has criticised repeatedly for its security record, said the solutions were not as simple as she suggested.
"I've heard Madame Le Pen saying again recently that with her in charge, certain attacks would have been avoided."
In the Elabe poll, both conservative Francois Fillon and hard-left candidate Jean-Luc Melenchon were seen narrowing Macron and Le Pen's lead over them.
Provided Macron and Le Pen do make it to the second round, the former economy minister was projected to win with 65 percent against 35 percent for Le Pen, the survey for BFM TV and L'Express magazine showed.
The poll found that Macron was set to win 24 percent of the vote in the first round and Le Pen would get 21.5 percent, with his score steady from the last time it was conducted three days earlier while hers was down 1.5 percentage points.
Fillon, who has slowly clawed back some ground lost after being hit by a fake jobs scandal, saw his score in the first round rise half a percentage point to 20 percent.
Melenchon, who would hike taxes on the rich and spend 100 billion euros ($107 billion) of borrowed money on vast housebuilding and renewable energy projects, gained 1.5 points to 19.5 percent as he built further on momentum he has seen after strong performances in television debates.
If Melenchon makes it to the runoff, he is projected to beat both Le Pen and Fillon by comfortable margins although he is seen losing to Macron 41 percent to 59 percent.
The number of people surveyed who expected to definitely turn out for the first round rose to 71 percent, the highest so far during the campaign although that is nonetheless low by historical standards.
($1 = 0.9336 euros)
(Additional reporting by Laurence Frost; Editing by Andrew Callus)
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