WASHINGTON — A former Massachusetts governor, Mitt Romney, who has taken the lead in the early Republican presidential contests by convincing social conservatives he has changed his position on issues such as abortion, is now focusing on economic matters, especially taxes.

He has tough competition. Mayor Giuliani, who maintains a healthy lead over all other Republican candidates in national polls largely because of his anti-terrorism image, also is stressing economic issues.

Mr. Romney said in an interview on Tuesday that he would make President Bush’s tax cuts permanent and lower corporate tax rates. He also said the American government should “take a good, hard look” at implementing a consumption tax.

Mr. Romney made clear he opposes efforts to boost taxes for managers of private-equity firms, who often pay a lower rate than middle-income Americans. “I’m trying to bring taxes down,” he said. “I’m not going to be in favor of a proposal to change something which is a capital gain and turn it into ordinary income,” he said.

He also said the U.S. Federal Reserve is taking the right steps to address turmoil in world markets triggered by the subprime-mortgage collapse and housing defaults. Mr. Romney, who made millions as co-founder of a private equity firm, Boston-based Bain Capital LLC, before becoming governor, is betting he’ll be able to leverage the economic issue as the campaigns kick into high gear after the Labor Day holiday.

Much of the focus on his candidacy has been on issues that appeal to the party’s base, such as abortion, guns, and immigration, all topics on which his tone has shifted since he was governor of Democratic-dominated Massachusetts.

The abortion issue resurfaced this month when Mr. Romney said in an ABC News interview that he supports a human life amendment to the Constitution that would protect the unborn. The statement conflicted with his earlier statements in favor of allowing the states to decide on the legality of abortion.

On Tuesday, Mr. Romney sought to clarify his remarks, describing calls by Republican Party politicians for a federal ban on abortion an “aspirational view.”

“I would love to see us not have abortion in this country, but that’s not where the American people are,” Mr. Romney said. “Therefore, I believe the right course for us at this point is to see Roe v. Wade overturned and to allow states to have returned to them the abortion matter.”

Most state surveys show Mr. Romney is ahead of his Republican competition in Iowa and New Hampshire, which are scheduled to hold the first caucus and first primary of the presidential-election calendar.

He disputed public surveys showing he is trailing in South Carolina, which traditionally holds the first Southern primary. Some experts say he’s lagging there because the state is more conservative and voters are critical of his changed position on abortion and of his Mormon religion.

An American Research Group poll conducted July 26–30 found Mr. Giuliani and a former Senator, Fred Thompson, virtually tied, at 28% and 27%, among Republican primary voters in South Carolina. Mr. Romney was at 7%. Like Mr. Romney, Mr. Giuliani is increasingly putting his emphasis on economic issues.

On Saturday in New Hampshire, he detailed his tax plan. It includes lowering marginal rates and reining in the growth of the alternative minimum tax, the levy that was originally intended to ensure that wealthy people paid their fair share, but which now threatens to ensnare millions of middle-class taxpayers.

Like Mr. Romney, Mr. Giuliani tried to emphasize his commitment not just to holding the line on current taxes, but to further cutting rates. “It’s not just theory for me, because I cut taxes and got results as mayor of New York City,” he said.

Pat Toomey, head of the Club for Growth, which advocates limited government, enumerated what he said were Mr. Giuliani’s greater achievements: “More tax cuts, more restraint on spending, he sold off and privatized activities of the government, and he was able to reduce the welfare rolls dramatically.”

The group’s analysis of Mr. Romney’s economic record said it “contains a mixture of pro-growth accomplishments and some troublesome positions that beg to be explained” on taxes. That includes his past opposition to the flat tax, the group said.

Mr. Romney also addressed the guilty plea of Senator Craig of Idaho, a Senate liaison for the campaign, for disorderly conduct, related to his arrest in connection with complaints about sexual activity in a men’s room at a Minnesota airport.

Mr. Romney said he can’t account for the behavior of all his supporters. “I don’t think it reflects on me,” he said. “I don’t know the particulars of this case and, you know, wish him well.”

A short while later, during a CNBC television interview, Mr. Romney called Mr. Craig’s behavior “very disappointing.”