Even though it's been more than a year since this posted, these are my thoughts exactly.
(Color based upon the Party of the President)
2014 -- huge R gains against a President with middling approval
2010 -- huge R gains against a President with middling approval, changing the majority party
2006 -- huge D gains against a President rapidly becoming unpopular, changing the majority
2002 -- slight R gain in the wake of September 11
1998 -- slight D gains, but not enough to undo the R majority
1994 -- huge R gains against a President with middling approval, changing the majority party
1990 -- slight D gains strengthening the D majority
1986 -- slight D gains strengthening the D majority
1982 -- slight D gains strengthening the D majority
1978 -- slight R gains but not enough to change the D majority.
If there is any pattern, Americans seem to like split government.
This is what I think will hold true for 2018
House elections. But the Senate is another story. The Dems have too many disadvantages going into next year's Senate elections, and I think they will inevitably lose 4 or 5 seats in Senate, even while they gain seats in the House.
