TITLE: "Wrong Choice."

LENGTH: 30 seconds.

AIRING: Cable and broadcast stations in Illinois.

KEY IMAGES: This ad by Republican presidential candidate Mitt Romney takes sharp aim at chief rival Rick Santorum's economic plan, claiming the former Pennsylvania senator is an "economic lightweight" on par with President Barack Obama.

With soft music in the background, a narrator asks: "Who can turn around the economy and defeat Barack Obama?" and quickly adds: "Not Rick Santorum."

"Santorum's real weakness is the economy," the narrator says as the screen shows jumpy footage of Santorum talking with a background image of an abandoned factory.

"He's never run a business or a state. His plan: `economic illiteracy,' `inexcusable,' `the worst idea of any GOP candidate.'" There's a shot of a toddler in a crib as the narrator calls Santorum's plan "economic illiteracy."

"Rick Santorum: Another economic lightweight," the narrator says as the screen shows side-by-side shots of Obama and Santorum. "Mitt Romney: Ready to `lead the nation to a new era'" and "with `the boldest GOP agenda since Reagan.'"

The ad closes with a beaming Romney meeting with workers and greeting an enthusiastic crowd from a stage.

ANALYSIS: In the final days before the hotly contested Illinois primary, Romney is trying to drive home his point that he is better equipped to lead the nation's economic recovery, the thematic foundation of his candidacy. Romney wants to regain a jolt of momentum in the large industrial state while stopping the surging Santorum, who has been buoyed by a pair of victories over Romney in the Deep South states of Alabama and Mississippi.

As in several past contests, Romney and his allies are spending heavily on attack ads to gain an edge.

Romney bases his latest claims almost exclusively on commentary in various media that are included in small text that can be difficult to read as it scrolls across the screen. A line that Santorum's "real weakness is the economy" comes from a headline on the financial website MarketWatch.

The line about Romney being "ready to lead the nation to a new era" is from the Cincinnati Enquirer's endorsement of him. The closer about Romney having the "boldest GOP agenda" since President Ronald Reagan was pulled from an opinion piece by a blogger for the American Enterprise Institute, a conservative think tank.

Romney, as a former governor of Massachusetts with a long record as a venture capitalist, is trying to play up his economic background by noting that Santorum, who spent much of his career in Congress and as a media commentator, has never run a business or a state.

Romney has played up his business background as proof that he has the know-how to turn around the nation's ailing economy, and the ad tries to build on that assertion. Santorum often highlights his socially conservative views.

The former governor favors lower taxes, less regulation, a balanced federal budget and more trade deals to spur growth. He would replace jobless benefits with unemployment savings accounts. Santorum wants to spur job creation by eliminating corporate taxes for manufacturers, drilling for more oil and gas, and slashing regulations.

Romney and other rivals for the Republican presidential nomination have accused Santorum of turning his back on fiscal conservatism when he was a senator from Pennsylvania by supporting big-government spending programs. Santorum has countered by saying he is the true conservative in the GOP pack.