In 1998, after the Republican Party grew unpopular in the wake of the Clinton impeachment trial, Democrats had some hope of winning the House. Democrats wound up gaining a few seats — far better than parties usually do in midterm years — but that may have been toward the upper bound of their plausible performances. The Senate, where the Democrats needed to gain five seats while defending more seats than the GOP, was another problem.
But relatively sleepy election years like 1996 and 1998 were fairly common in the past. The parties were in a long stalemate between 1980 and 1992, with Republicans controlling the presidency and Democrats retaining a large edge in the House.
Back then, at least, the parties behaved in a more bipartisan fashion. So the outcomes were less binary, and the margins of control in the House and the Senate mattered more. Ronald Reagan and George H.W. Bush were far from being lame ducks at this time in their tenures.
The caution, of course, is that all of this is easier with the benefit of hindsight.