Portman, during an interview with The Hill, said he was satisfied with the Bush administration's second-term effort to curb spending while trying to keep his work with the unpopular president at arm's length.
Portman, who was Office of Management and Budget director from May 2006 to August 2007, recalled his skirmishes with other senior advisers, The Hill first reported Thursday.
"I was frustrated when I was there about some spending issues -- specifically, as you know, I wanted to offer a balanced budget over five years, and a lot of people didn't," he said. "I prevailed. The president sent his budget -- not my budget, his budget -- a five-year balanced budget. But it was a fight, internally."
Portman also was Bush's U.S. Trade Representative before heading OMB.
Portman says he won another debate within the administration and with lawmakers over posting earmarks on the Internet, a change he said was needed to create greater transparency.
"We also took some heat on putting all earmarks online, both internally at the White House and up here. We won that fight. So I felt I was making progress," he said.
Former Bush administration officials told The Hill Portman was the top advocate for fiscal discipline before budget-cutting became the current mantra within GOP circles.
"Rob was, I argue, the leading proponent of balancing the budget and fiscal restraint during the time I was there," said Edward Lazear, chairman of Bush's Council of Economic Advisers from 2006 to 2009.
GOP strategists said they think Romney will have to run against Bush's spending record, meaning Portman would have to do the same if he is selected as the vice presidential candidate, Politico said.
"Romney has to run a little bit against Bush as well as against [President] Obama," said Grover Norquist, president of powerful Americans for Tax Reform. "He needs to say, without being insulting, that the Bush years were ones of too much spending."