A vote to roll back insurance regulations of the Affordable Care Act may represent the most decisive turning point of the Obama presidency. Thirty-nine Democrats—more than a fifth of all Democrats in the House—joined united Republicans in voting to allow insurance companies to write the same policies they offered before passage of Obamacare.

For the first time, Democrats are deeply divided, with significant numbers ready to defy their leaders on Capitol Hill and in the White House. If the GOP can maintain its unity on key issues, and not become distracted by ego-driven jockeying by presidential prospects, conservatives can press this advantage.

The key to political victory is always uniting your own side while dividing the opposition. The ongoing fight to spare Americans from the disruptions and dysfunctions of Obamacare enables Republicans to do just that.