Landslide victories don't really exist anymore. We aren't in the 80's. The demographics have changed. Whites vote overwhelmingly for Republicans, and minorities for Democrats. A Republican can never win a state like CA or NY no matter who the Democrats nominate.
If Trump beats Bernie, it will be with similar margins to 2016.
Although a Republican wont win NY or CA in the next few generations, there are plenty of states that can go to Trump over a socialist/communist like Sanders such as NH,ME,NV,CO,VA,MN and even NM.
I could be wrong on the math but thats 344 to 189.