It’s spring in Washington, and time to resume one of the capital’s favorite sports. No, not baseball, but throwing mud at the Supreme Court. Pending cases include the legal status of same-sex marriage and whether the IRS can provide billions of dollars in Obamacare subsidies without explicit congressional authorization. Partisans have launched a preemptive bid to undermine the legitimacy of the forthcoming decisions by accusing the court of “activism” for involving itself at all.

These increasingly transparent attempts to discredit the court should be rejected.Every case involving plausible abuses of power requires judicial engagement — conscientious, impartial truth-seeking, grounded in evidence — rather than reflexive deference to the political branches.

Take the Obamacare case. At issue in King v. Burwell is a section of the Affordable Care Act concerning tax credits for buying health insurance from government-operated healthcare exchanges. Congress wanted states to set up their own exchanges, but it lacks constitutional authority to force them. So Congress opted for a stick-and-carrot approach, authorizing tax credits for insurance policies purchased “through an Exchange established by the State.” As a backup, the ACA directed federal bureaucrats to set up federally operated exchanges in states that declined to set up their own.