Gross said that if Jacobs runs, his record in business would appeal to voters and said he didn't think the time outside the state would be viewed as a negative.
"I don't think we're an island," Gross said. "We have other people who have spent a good deal of their careers outside the state."
If no candidate gets 35 percent of the vote in the June primary election, the nominee will be selected at a GOP convention. But Gov. Terry Branstad said he thought the race would be decided in the primary.
"I think the more they get a chance to evaluate the candidates, we'll see somebody emerge," said Branstad, who has not endorsed a candidate, though Lt. Gov. Kim Reynolds is backing Ernst.
The Iowa Senate race is expected to be closely watched, as Republicans try to retake control of the U.S. Senate. The GOP needs six seats to regain the majority, and have some opportunities in states like Iowa where there have been Democratic retirements. But thus far Republican-leaning groups are spending less for the 2014 cycle than they did ahead two years ago.
Still, Republican pollster Greg Strimple said Democrats like Braley could have a tough time in 2014, given the rocky rollout of President Barack Obama's health care overhaul.
"Right now, I don't want to be the guy defending the ObamaCare law," Strimple said.