No crystal ball required. It's obvious. The liberals are self destructing. They are becoming more violent, killing cops, beating people up at political rallies, spewing hate at every opportunity. They are finished. Americans aren't stupid. They are watching everything you fools do. And they don't like it. The democrats will lose because they are doubling down of the same behavior that lost them the last election. Besides, Trump will turn things around. That's the real reason you guys will lose. Your party has been soundly rejected. You have lost the White House, both houses of Congress, as well as countless Governors and state legislatures, and Trump will likely appoint at least one more Supreme Court judge. You guys are history.

you can't even discern the difference between "Liberals" and "Democrats", conflating both of them with "leftists".
Here's the main reason you're clueless, clown shoes. You can't predict what happens in a mid-term
a year and a half out. You need to wait for, say, October 2018 to do that. By then anything happening now will be ancient history. Unless it's a big thing like the Russia investigation.
Here's the other perspective you're lacking: It's a mid-term.
In this country whichever party holds the White House
nearly always loses ground in the mid-terms. There have been tree exceptions to that in the entire time the Duopoly has existed -- a century and a half. So if we have any indication at all at this point ----- there it is.