Supporters and opponents of referendum questions on the November ballot in Maine have spent more than $2 million so far on television ads.

Data released Thursday by the Center for Public Integrity show indicates more than 4,000 ads have aired on four proposals – to expand background checks, legalize marijuana, boost the minimum wage and tax wealthy Mainers to help schools.

The analysis shows $1.3 million has been spent on more than 2,500 ads on the referendum to expand background checks for gun purchases.

More than 1,000 ads have aired aimed at the school-funding proposal, and there have been 681 ads on the marijuana referendum.

The figures cover spending through Monday and don’t include ads that aired on cable television, radio or online.