I have long held that trying to win elections by moving to the middle is the wrong strategy. The GOP wins elections when their base is motivated to turn out and vote for candidates that advance the conservative values.
That's exactly what the Democrats have been doing since November 2016.
The last few special House elections (including this one) have featured Democrat candidates running on a promise to vote AGAINST Nancy Pelosi as House Speaker. They've been pretty successful using this approach to flip Republican seats.