But the polls show a four-way race has developed between her, Emmanuel Macron; François Fillon, the scandal-scarred conservative candidate; and Jean-Luc Melenchon, far-left firebrand.
Voters will cast their ballots on Sunday in the first round of what has transformed into the most unpredictable French election in living memory, with four candidates within reach of the two places in a run-off a fortnight later.
Hundreds of protesters have marched in Marseille against French far-right presidential candidate Marine Le Pen, ahead of her final rally in the southern port city. The top two candidates will meet in a runoff on May 7.
Gaspard Flamant says he fears Le Pen will win the election's first-round vote. A defeat by Hamon could crush the party of unpopular Socialist President Francois Hollande, who chose not to seek a second term.
Her rival candidates were happy to let "immigrants turn France into a enormous squat", she argued.
Macron is the only candidate so far to have said he has talked with Obama, a popular figure in France. Authorities announced Tuesday that they had arrested two Islamic radicals suspected of plotting a possible attack around the vote.
She assailed recent governments for failing to stop attacks and warned on BFM television earlier in the day; "We are all targets - all the French".
What is at stake in this election is the continuity of France as a free nation, our existence as a people, she said in February 2017.
Le Pen, who wants to withdraw France from the European Union and do away with the euro currency, defended her decision to force national news network TF1 to take down the EU flag during an interview Tuesday night.