Both candidates have a case to make between now and the runoff in April and may moderate their positions to lure the other 50% of voters. But there's no guarantee of that. Depends on what strategy they try to run.
For Vallas, he may tone down the crime/cops talk since he's already got that issue locked up. But many Lightfoot, Garcia and Wilson voters care about crime too, so there could be a payoff for keeping his foot on the gas. Hopefully Vallas comes forward with some real solutions/ideas, which shouldn't be too hard for him if he's as wonky as he claims to be.
Johnson has a harder road. He dominated the progressive lane, but that's only 20-25% of the city max. I think he
hinted at his strategy in his speech tonight - he will try to mop up the Black vote from Lightfoot, Wilson, Green, Buckner, King, Sawyer. That progressive/Black coalition is how Harold Washington won... But key to that is getting the votes from more conservative elements in the Black community. So he'll probably stress Black solidarity over the next month and focus on feel-good stuff in the community instead of divisive politics.
I'm probably leaning Johnson now, I really hate Johnson's tax plans but he has some great parts of his platform. Vallas has given me nothing to like, his platform is vaporware and buzzwords except for the crime & cops talk. Johnson's CTU support is problematic, but Vallas has basically an identical relationship with FOP at this point which is just as bad or worse. (Only one union is out there killing Chicagoans, and it ain't CTU)