Caught this on www.mediaite.com/… :
The Sanders campaign agreed to the debate and the Trump campaign was “very intrigued” with the idea.
However, “before the debate could be announced, the Trump campaign pulled out, citing scheduling conflicts, so the network planned to welcome just Mr. Sanders in an hourlong town-hall-style event, hosted by Bret Baier as part of his ‘Special Report’
Sourcing the New York Times :
the network had an outside-the-box idea last month that would have made primary debate history: a face-off between Senator Bernie Sanders of Vermont and the equally fiery candidate on the Republican side, Donald J. Trump.
I guess we’ll have to wait until Bernie comes back in this northern swing to win the pledged delegates and the nomination to see this.