Haley Barbour: Obama's cash will let him define Romney

Barbour, who is involved with the Republican-affiliated outside groups American Crossroads and Crossroads GPS, suggested that if Obama goes on the attack before Romney is prepared to defend himself, the super-PACs would provide some air coverage for him.

"Everybody who wants a new president wants to keep the voters' attention on those policies and the results of those policies," Barbour told The Hill.

The groups have already raised a combined $100 million and have millions in cash on hand. They've been running ads attacking Obama for months, including an ad released this morning that attacked Obama's appearance on the "Late Night with Jimmy Fallon" TV show.

The Obama campaign team has around $100 million cash on hand, according to April fundraising reports, while Romney has about $10 million cash on hand. Romney and the Republican National Committee recently announced a joint fundraising effort.