The 2022 presidential election was an almost perfect 3-way split between the left, the neoliberal right (Macron+Pécresse) and the nationalist far-right (Le Pen+Zemmour+NDA). This meant that in theory, with the right vote distribution, any of these three factions could have qualified for the runoff. However, Mélenchon is at somewhat of a disadvantage, since many people on the left hate his guts and would probably not vote for him against Macron. So unfortunately Macron probably wins no matter what. There will not be a clear alternative to Macron unless either the left gets its sh*t together and nominates a candidate who isn't extremely divisive, or the dam against FN finally breaks and Le Pen actually wins.
One thing to note is that Le Pens trying to get left wing votes alienates the Zemmour wing who is much more right wing economically . Le pen exceeded her factions vote share in the 2nd round in most areas except very strong Zemmour areas.
That's because Zemmour was only marginally taking from the previous election's Le Pen voters - and mainly in the south. That's what he thought would occur. Instead, his coalition pulled more from LR because he resembled those voters even though he said a bunch of racist stuff. Which is one reason why Ciotti was so brazen during his leadership bid and still won. It seems weird but a large chunk of those Zemmour voters in I-d-F already went Macron in round 2.
I’ve actually met two Zemmour-Macron voters, one of whom phrased his decision to vote Macron in round 2 as being a vote against Le Pen “the socialist”.