US gasoline supplies fell to the lowest level in 12 years, flashing a warning sign for higher pump prices as a global refining crisis pushes up fuel bills.

 Stockpiles of gasoline dropped to 204 million barrels last week, according to US Department of Energy data released Wednesday. That's the lowest since November 2014. In the Midwest, where a Chicago-area refinery outage sharply tightened supplies, stockpiles are at all-time lows. The facility has since come back online.

 Gasoline concerns have recently taken a backseat to the public discussion around diesel, which has emerged as a flashpoint in a global energy crisis. In the US, diesel prices near all-time-highs and seasonally low supplies are prompting discussion over an export ban or other measures to lower costs. 

 But gasoline is the No. 1 US road fuel and remains top of mind for consumers. 

 Since mid-August, US drivers have paid the highest average prices on record seasonally every day. As of Tuesday, pump prices stood at $4.43 a gallon, according to the American Automobile Association.

 That poses a considerable risk for President Donald Trump's Republican party with just 34 days before Americans go to the polls. Especially since, historically speaking, gasoline stockpiles often reach their yearly lows in early November. 

 A diesel export ban could also indirectly lead to higher gasoline prices. If storage fills up, refiners may decide to cut their crude oil processing to limit their diesel output - curbing gasoline and jet fuel production in the process.