Democrats begin campaign season on offense. President Biden is piling up legislative victories, benefiting from falling gas prices, and slamming “MAGA Republicans” as a threat to democracy. At this writing, Democrats have caught up with the GOP on the congressional generic ballot. They have done well in the four special elections since the Supreme Court overturned Roe v. Wade. Their Senate candidates are either tied with or ahead of Republicans in battleground states. Republicans remain the favorites to take control of the House, to be sure. But the Senate is a jump ball, and governor’s mansions in Wisconsin, Michigan, and …