Mitt Romney is looking to build momentum after winning the Michigan and Arizona primaries Tuesday.
Romney scored a hard-won but narrow home state triumph and powered to victory in Arizona, the Star Tribune said. The Republican presidential race now expands to the 10 states that will vote on Super Tuesday.
Romney's slight edge - 41 percent to Rick Santorum's 38 percent - raised questions about whether he would change his strategy, the article said.
"We didn't win by a lot, but we won by enough," he told supporters in Michigan.
Romney said he had made personal mistakes in recent weeks and was trying to "do better and work harder."
Romney signaled Tuesday night that he intends to stick to his core campaign message of fixing the economy and reducing unemployment.
"More jobs, less debt and smaller government - you're going to hear that over and over in the states ahead," he said.
The victories earned Romney about three-quarters of the delegates at play Tuesday night, extending his numerical lead over his opponents, the New York Times said. Romney won all 29 of Arizona's delegates and about half of those in Michigan, where the final allocation was still being worked out.
The Times said that Romney's twin victories over Santorum have quieted - for now - what had been growing questions about his command of the Republican field and his ability to appeal to the conservative base of his party.
All four candidates face financial strains as they try to advertise in a slate of expensive states, the Tribune said. Costs to run a week's worth of ads across the states voting next week are estimated to be about $5 million.