President Barack Obama's campaign has spent nearly $100 million on television commercials in selected battleground states so far.

The sustained early barrage is designed to create lasting, negative impressions of Republican rival Mitt Romney before he and his allies ramp up for the fall.

More than one-fifth of the president's ad spending has been in Ohio, a state that looms as a must-win for Romney more so than for Obama. Florida ranks second and Virginia third. That's according to organizations that track media spending and other sources.

About three-quarters of the president's advertising have been critical of Romney. Obama's television ad spending dwarfs the Romney campaign's so far by a margin of 4-1 or more.

(Copyright 2012 by The Associated Press. All Rights Reserved.)