(MCT) — WASHINGTON — After a final cross-country campaign whirl by both candidates, President Barack Obama heads into Election Day riding a slim lead in enough key states to secure a second term, while Mitt Romney remains competitive and could yet unseat him.

National polling showed late voter movement toward Obama, raising the possibility that the election might not drag out for days and weeks of wrangling over disputed ballots, as some feared. The president continued to maintain a slight edge in the vast majority of swing-state opinion polls, though his advantage typically remained within the surveys’ margins of error.