Depends whether or not the pro-Trump left manages to demonize him and brainwash progressives against him like they did Clinton. If he can avoid that, then he should be heavily favored.
You're like a parody of a Clintonista.
First of all, the "pro-Trump left" isn't really a thing. Sure, a few "leftists" here and there chose to support Trump, but that was more out of a desire to spite the Democratic Party and to send a big fat "f-you" to the Democratic establishment in Washington. And although I believe their support for Trump was misguided, it's hard to argue that they didn't achieve their goal.
A fire has now been lit under the asses of the Democratic establishment and the activist base of this party is fired up and ready to take over congress, governors mansions, and state houses all over the country in 2018.
Booker is not the ideal candidate for Democrats in 2020, and it's really not hard to understand why. He's despised by the Sanders wing of the party, plain and simple. Democrats need a candidate who can please both the Sanders and Clinton wings of the party. A candidate like Elizabeth Warren, Sherrod Brown, or Jeff Merkley.