He won't and he shouldn't.
Countries that have major political jumps always have a corresponding backlash and it leads to legislation being all over the place and the culture wars stuff. The right way to skin this cat is slowly and rationally.
If he goes fully on left wing then he just feeds ammo to the crazies. Like with most things, measured and slight movements that accumulate over time are much preferable to large swings. That's how we got here and realistically it's the only way to move the spectrum while still remaining electable. Because if you're unelectable then this is mostly academic.