Mitt Romney’s presidential campaign on Monday rejected a Republican attack on the Affordable Care Act, repudiating a contention made in last week’s Supreme Court decision that the law’s requirement that individuals carry medical coverage amounts to a tax. The Romney team’s refusal to invoke the word “tax” with regard to the individual mandate puts the candidate at odds with others in his party at a moment when Republicans are attempting to capitalize on the Supreme Court’s decision, which deemed President Obama’s health-care law constitutional. Some Republican-led states are trying to thwart the legislation’s effort to cover the poor. In an...