Liberals who underestimate Newt Gingrich still don't realize why Democrats lost 1994, 2004, 2010, 2014, and 2016.
Democrats should not get too overconfident. The 2018 map favors Republicans because of the conservative lean of these states and the fact that older, whiter, wealthier people turn out more than younger, minority, poorer people.
2018 is a Lean D year, but anything could happen from now and the week of Nov. 4, 2018.
You forgot 1998, 2000, and 2002, which were also years Democrats suffered classic wipeouts. Unfortunately in most elections since 1980 (The year Ronald Reagan Destroyed America) Democrats have been blowing it badly with the exception of when Bill Clinton and Barack Obama were on the ballot (what's funny is that before 1980 neither of them would have been considered real Democrats) or in 2006 after little Bush let his Saudi buddies murder over 3000 innocent Americans so he could invade Afghanistan and Iraq which would lead to the deaths of around 6000 American soldiers and hundreds of thousands of innocent Iraqi and Afghan civilians, so that should tell you what Republicans have to do in order for the majority of bigoted White Americans to suck it up and put Democrats back in charge of the US government.