WASHINGTON (AP) — Deep-pocketed donors are turning over multimillion-dollar checks to influence November’s elections, and the sums raised by the national parties and their super PAC allies are already approaching the $1 billion mark, according to financial reports still being filed Tuesday evening.

An imprecise snapshot of political giving is coming into focus as outside organizations detail their fundraising and spending through March 31. The enormous sums of money do not capture what federal candidates themselves are raising and spending. In other cases, some of the most active outside groups operate under rules that allow them to keep many details of their finances secret.