A year after the federal Affordable Care Act took effect, California voters are now considering another major change to health care: a ballot measure that would give state officials the authority to veto health insurance rate increases for individual and small group plans. Proposition 45 would hand broad new control of the individual health insurance market to the state insurance commissioner, who could reject rate increases deemed excessive. The measure is designed to keep costs down for consumers in a state where health care premiums have spiked in recent years, raising public ire.