Mitt Romney left his GOP rivals behind to focus solely on criticizing President Obama's economic policies while campaigning in Wisconsin the night before the state's primary -- as Rep. Paul Ryan voiced confidence that Romney will secure the GOP nomination against Rick Santorum.

During separate interviews for "On the Record with Greta Van Susteren" Monday night, Romney and Ryan both emphasized the need to turn around America's economy and the critical role the issue will play during the general election.

"The president has failed when it comes to caring for the American people," said Romney. "This president's policies have failed. His economic policy has been a bust."

Romney did not speak a word about his GOP rivals during the interview. Ryan, though, said Santorum is not capable of attaining the delegates he needs to win the nomination -- he said Santorum would need about 82 percent of remaining delegates if Romney sweeps the three contests held Tuesday.

"I don't see how he can put it together," Ryan said about Santorum. 

Ryan also said he thinks Romney has the best chance of beating Obama in the general election.

In a attempt to temper the criticism and possibly distract from the primaries in Wisconsin, Maryland and D.C., Obama planned to make another major economic speech Tuesday at an Associated Press luncheon to address his economic policies. Obama will focus on tax fairness, shared responsibility and the "Buffett Rule," and is expected to sharply criticize a $3.5 trillion budget proposal pushed by Ryan last week.

Ryan did not mention Obama's planned remarks. But he urged the party to move toward the nomination end game. 

"The primary has been productive but we are moving to the counterproductive stage," said Ryan. "If this drags out longer it will be that much harder to beat Obama in the fall." 

Santorum has said he plans on continuing his campaign regardless of the outcome in Wisconsin Tuesday.