Trump’s support is not merely Democrats. Plenty of disaffected Democrats who do not like what Bernie or Hillary are selling (at least this week) are among his support (at least in the primary, just as Democrats primary voted for McCain in 2000 and 2008).
I don’t trust the dems, they have changed their party affiliation many times from D to R in the primaries and then going back to D in the General election. The only exceptions were the election and reelection of President Reagan
Democrats crossed over to vote for McCain in the 2000 and 2008 primaries because they thought he’d be the easiest to beat in the general election. Democrats put the interests and agenda of the Democrat Party first and foremost...always.