Macron swept away far-right candidate Marine Le Pen to win the presidency on May 7th, but has only achieved half the job.
Macron's Republique en Marche (Republic on the Move, REM) party, which he only founded in April 2016 as a platform for his presidential bid, now needs a commanding majority in the National Assembly for him to implement the reforms he promised on the campaign trail.
A host of opinion polls show Macron's party could take around 30 percent of the first-round vote on Sunday, which would put it in pole position to secure an absolute majority in the second round a week later.
That could equate to as many as 400 seats in the 577-seat chamber.
"A wave or a tsunami?" asked the front page of the leftwing daily Liberation on Saturday.
REM has already had a boost after its candidates came first in 10 of the 11 French overseas constituencies that have already voted.
The legislative elections are, like the presidential contest, held over two rounds.
If no candidate wins over 50 percent in the first round, the two top-placed go into the second round - as well as any candidate who won the votes of over 12.5 percent of the electorate.
Breaking the mould
French voters have traditionally rallied behind their new leader in the legislative elections that always follow the presidential ballot.
Macron's predecessors Francois Hollande in 2012, Nicolas Sarkozy in 2007 and Jacques Chirac in 2002 all won outright majorities. Unlike Macron, however, they all came from long-established parties.
REM has broken the mould of French politics. Initially dismissed by Macron's opponents as a movement of metropolitan bright young activists without any real roots, it will field 530 candidates on Sunday.
In a bid to renew the political scene, many have never stood for office before, such as Marie Sara, a rare female bullfighter, who is taking on a senior member of Le Pen's National Front in southern France, Gilbert Collard.
Some observers suggest Macron's candidates are merely riding the wave of popularity of the new president and may offer little opposition to their boss once they are elected.
"If I may say, at the moment you could take a goat wearing a Macron badge and it would have a good chance of being elected," BFMTV political commentator Christophe Barbier said this week.
Cleaning up politics
Macron has banned all the REM candidates from employing family members if they are elected and they must not perform consultancy work while lawmakers.
The edicts follow the scandal that sunk the presidential chances of Francois Fillon, candidate for the rightwing Republicans party, who is facing criminal charges for paying his wife Penelope more than €900,000 ($1.0 million) as his parliamentary assistant. Fillon denies the accusations.
Given Macron's attempts to clean up French politics, he faced embarrassment on Friday when his small centrist ally, the MoDem party, was placed under preliminary investigation on suspicion of employing fake parliamentary assistants at the European Parliament.
The investigation comes with one of Macron's ministers, Richard Ferrand, also being probed over suspicions he favoured his wife in a property deal with a public health insurance fund when he headed the company.
Macron's party has brushed off the accusations against Ferrand as unfounded.
With the political tide turning against the main parties of left and right, they have warned that a landslide could be bad for democracy.
"I don't think it would be healthy for the democratic debate over the next five years," said Francois Baroin, who is leading the Republicans as they try to bounce back from Fillon's failure in the presidential election.
Le Pen defiant
Le Pen's party meanwhile looks set to struggle to win 15 seats nationally, a score that would represent another deep disappointment after she was soundly beaten by Macron in the presidential election.
Le Pen was defiant when interviewed by AFP this week, saying: "We will be the only opposition force."
Macron has appealed to voters to give him a strong mandate to overhaul the labour market whose rigid rules on hiring and firing hold back the economy, according to many experts.
The president was economy minister in the previous Socialist government that began introducing the reforms, sparking mass demonstrations for months last year.
By Sylvie Grout and Guy Jackson