AMES, Iowa — Mark Warner, a potential 2008 presidential candidate, voiced growing concern yesterday with his party’s electoral strategy, arguing that Democrats’ willingness to write off sections of the country could make it nearly impossible to win the White House.

“I got pretty frustrated after 2004,” the former Virginia governor said. “We are making a mistake if we put up candidates that are only competitive in 16 states, and then we roll the dice and hope we win Ohio or Florida.”

In an interview with the Associated Press, Mr. Warner insisted he was not being critical of 2004 Democratic nominee John Kerry, whom he called “a very strong candidate.” But Mr. Warner said Democrats must stop conceding entire regions of the country.

“We do our party and the country a disservice if we’re not competitive in the South and the balance of the Midwest,” Mr. Warner said. The Democratic National Committee chairman, Howard Dean, has steered money and staff to all states, contending that the party needs to build its operation in Republican bastions.

Mr. Warner spoke after a campaign appearance in Ames, home of Iowa State University and a popular spot for Democratic contenders. To be successful, he said, Democrats must reach beyond bastions such as college towns.

“We’ve got to have candidates who can campaign not only in Ames but at NASCAR races, candidates who can campaign in the barrio and changing communities,” Mr. Warner said.

Mr. Warner spoke during a two-day campaign swing in the state where caucuses traditionally launch the presidential nominating process. He has been focusing on his core appeal to Democratic activists who are hungry for a nominee who can win back the White House after two losses to President Bush .

In making his case, Mr. Warner said he was elected governor in a state that has not voted for a Democratic presidential candidate since 1964, and last year, he helped get his Democratic lieutenant governor elected to replace him. In Virginia, a governor can only serve one term.

Mr. Warner argued that his success in Virginia came because he refused to give up on rural areas that traditionally vote Republican. He has taken the same approach in Iowa, spending Monday in heavily Republican western Iowa.

Mr. Warner also cited history, noting the success of Democratic governors such as Bill Clinton and Jimmy Carter.

“History has been pretty kind to Southern governors over the last 50 years,” Mr. Warner said.