There are plenty of reasons to believe that Democrats are headed toward a blue wave. Democrats are turning out in record numbers in primary contests even in “safe” races. They continue to over-perform in special elections, even flipping the state legislative seat that includes Donald Trump’s Mar-a-Lago estate.

Added to that, the war in Iran is already causing Trump to crater with groups of voters that had boosted him to reelection such as Latino voters. And most major pollsters show that voters would overwhelmingly vote for a generic Democrat for Congress compared to a generic Republican.

But one of the biggest indicators of an impending Democratic win come November is the number of Republicans in the House of Representatives not running for reelection.