A decisive vote to defend abortion rights in deeply conservative Kansas reverberated across the midterm campaign landscape on Wednesday, galvanizing Democrats and underscoring for Republicans the risks of overreaching on one of the most emotionally charged matters in American politics.

In a state where Republicans far outnumber Democrats, Kansans delivered a clear message in the first major vote testing the potency of abortion politics since the Supreme Court overturned Roe v. Wade: Abortion opponents are going too far.

The overwhelming defeat of a measure that would have removed abortion protections from the state constitution quickly emboldened Democrats to run more assertively on abortion rights and even to reclaim some of the language long deployed by conservatives against government overreach, using it to cast abortion bans as infringing on personal freedoms. (As of Wednesday, the margin was 58.8 percent to 41.2 percent.)