Skyrocketing energy bills are shaping up to be a cornerstone of congressional Democrats’ election-year message for why voters should return them to power in November.

The Trump administration is responsible for Americans’ bigger electric bills, Sen. Martin Heinrich (D-N.M.) said Thursday after a roundtable discussion on energy affordability with nine Senate Democrats, union, and local officials, and energy efficiency advocates. “That is what we communicate in the midterms. This is an open door; all you have to do is push on it.”

The issue is gathering steam, as extreme cold stretches across the US and more Americans confront eye-popping energy …