We focus on districts where Democrats cannot win due to gerrymandering or demographics, and ask, "What is the best value of each Democratic vote?" Is it to vote in a Democratic primary for a candidate who is going to ultimately lose? Or is it to choose the most moderate, reasonable Republican, who will wind up representing us?
We are a primarily a grassroots organization dedicated to ousting extremists in the Republican primaries. In most cases, we are only concerned with the primary election. We accept that some districts will be Republican, and focus on making sure those representatives are sane.
If a representative in a solidly red district proposes extreme bills, aligns with hate groups, repeals ballot initiatives, or supports President Trump, we think it is far more important to vote these people out than to choose a Democratic challenger who will ultimately lose.
The analysis is simple: look at the margin of victory in the last primary election, and look at how many Democrat, Independents, moderate Republicans, and others are in the district. In many, many cases, Democrats and Independents can vote as a block and sway the primary.