Analysts said that the shooting and the country's history of suffering terror attacks over the past two years would prove advantageous for the right-wing, anti-immigrant presidential contenders, particularly Marine Le Pen, who has been critical of "Islamist terrorism" throughout her election campaign.
It is unclear what impact the attack will have on the first round of already very unpredictable presidential elections on Sunday.
The two-round presidential election will take place on Sunday and May 7.
Investors have long fretted over the possibility that far right National Front leader Marine Le Pen would advance to the final vote. And if Trump isn't actually supporting Le Pen, the White House should probably take this opportunity to dispute that characterization.
Until now, Le Pen had struggled to get the campaign to focus on her party's trademark tough security and immigration stance.
There is concern that neither youthful independent centrist Emmanuel Macron, who lacks experience, nor centre-right former prime minister Francois Fillon, whose campaign was dogged by scandal, would have the vision or authority to bring change.
There are also structural factors that would restrain a President Le Pen or a President Melenchon.
As a candidate, Trump came under fire repeatedly for his rhetoric around immigration, including his promise to build a wall along the US's southern border with Mexico.
In an interview with The Associated Press, Trump said that while he is not explicitly endorsing Le Pen, the attack played to her strengths. None of the four front runners are expected to win the required majority needed to secure the presidency in just one round of voting. Some opinion polls still give a chance to the conservative candidate, François Fillon, but he is mired in a corruption scandal.
Surveys show a tight race between Le Pen and Macron, with Fillon and Mélenchon not far behind. French security is on high alert, expecting something to happen during the vote on Sunday.
"From this weak government of inaction I demand the immediate restoration of our national borders." she wrote, later adding, "I demand the immediate explosion of foreigners flagged for radicalization". Both Germany and Britain will also go to the polls over the coming months, but neither are as hard to read, or will potentially have such far-reaching consequences as the French election.
In an Elabe poll conducted on Wednesday and Thursday, and published on Friday, both Fillon and Melenchon were seen narrowing Macron and Le Pen's lead.