India, March 25 -- The Supreme Court's conservative majority sounded sceptical of state laws that allow the counting of late-arriving mail ballots, a persistent target of President Donald Trump. A ruling, likely to come by late June, that bars counting ballots arriving after Election Day would send officials scrambling in 14 states and the District of Columbia, just a few months before the 2026 midterm congressional elections to change their ballot rules.

An additional 15 states that have more forgiving deadlines for ballots from military and overseas voters also could be affected.

The legal challenge is part of Trump's broader attack on most mail balloting, which he has said breeds fraud despite strong evidence to the contrary and year...