WASHINGTON (AP) — An inflation gauge closely monitored by the Federal Reserve accelerated last month, showing that prices remain elevated less than a week from midterm elections in which affordability concerns have become a central issue.

Consumer prices rose 3.6% in September compared with a year earlier, the Commerce Department said Thursday, up from 3.4% in August. On a monthly basis, prices climbed 0.5%, up from 0.3% in August and the highest figure since May.

Annual inflation has worsened since the Iran war caused spikes in oil and gas prices. U.S. oil prices still top $100 a barrel, up from less than $70 before the war. Polls show that the rise in inflation has soured most voters on the economy and President Donald Trump's handling of rising costs. Trump campaigned in 2024 on reducing prices, including bringing the cost of gas below $2 a gallon. It currently averages about $4.25 a gallon nationwide.

Excluding the volatile energy and food categories, inflation also picked up. It increased 3.1% from a year ago in September, up from 3% in August. And from August to September, core prices rose 0.3%, the same as the previous month.