The 2010 election was a historic disaster for the Democratic Party. Republican House candidates won the national popular vote by 6.8 percentage points and took a commanding majority as a result. It marked the end of President Obama’s legislative agenda and the beginning of an era when Republicans demanded massive concessions just to keep the government open.
Now imagine that 2018 is the mirror image of 2010 — that is, that Democrats win the popular vote by the exact same...