Presidential hopeful Newt Gingrich has used op-ed pages, television interviews and his latest book to rail against Democrats for their use of congressional earmarking, calling it an “undemocratic, corrupt practice.”

But during his tenure as House speaker, Gingrich oversaw a dramatic expansion of the use of earmarks, laying the groundwork for a frenzy of itemized expenditures over the next decade, according to congressional records and interviews.

The surge was fueled in part by a political strategy, spearheaded by Gingrich, to help vulnerable Republicans keep their seats in the House. The period marked a crucial turning point in the use of earmarks, which until then had primarily been the province of a handful of powerful committee chairmen.

That history is likely to cause problems for Gingrich among influential tea party voters, who view earmarks as a symptom of spending excess and corruption in Washington. The issue is one of many challenges facing the twice-divorced candidate as he seeks support from religious and fiscal conservatives who hold sway in Republican primaries.

In one May 1996 memo, for example, Gingrich’s office asked powerful committee chairmen to include earmarks for members facing tough reelection bids that year — projects that would help them curry favor with their constituents.

“Are there any Republican members who could be severely hurt by the bill or who need a specific district item in the bill?” the memo asked, referring to appropriations legislation.

Over the next four years, while Gingrich was speaker, the number of earmarks doubled to more than 6,000 projects, while total earmark spending increased by more than 30 percent, according to data from the Congressional Research Service.

“If you take care of the members, they can take care of themselves back home. That was the philosophy,” said former Republican congressman Robert Walker (Pa.), who served as vice chairman of the House Budget Committee at the time. “It was a specific strategy and one I disagreed with. Instead of fixing the problem with earmarks, the Republicans spent a decade exacerbating it.”

Spokesman Rick Tyler declined to answer questions about the role of Gingrich and other Republicans in expanding the use of earmarks in Congress, but he characterized the issue as a systemic problem.

“The horse-trading that goes on in order to get members to vote the way leadership wants them to goes back to the Continental Congress,” Tyler said in a written statement. “More recently it had grown completely totally out of control which is why Newt called for a moratorium.”

Tyler added that “it will be a continuing fight because members will always seek to get legislation favorable to their districts.”

Gingrich has stumbled through a series of controversies since announcing his presidential candidacy last month, including a firestorm over his criticism of GOP Medicare plans and disclosure of up to $500,000 in past credit at the luxury jeweler Tiffany & Co.

Matt Kibbe, president of FreedomWorks, a Washington-based advocacy group that works closely with tea party groups, said Gingrich’s role in encouraging the use of earmarks is among “a number of key issues” that could hurt the former House speaker with tea party voters.

“I think that poses a real problem for him,” Kibbe said. “For the tea party, earmarks have become a symbol of the culture of spending. You can either be on the right side or the wrong side of that issue, and this looks like the wrong side.”

Earmarks are amendments to legislation that direct funds for specific projects, often in the home district of the member requesting them. The use of earmarks took off under Gingrich and continued to escalate over the next decade, peaking at $31 billion for 11,320 projects in 2010, according to congressional data.

Many earmark projects, such as a so-called “bridge to nowhere” in Alaska, became widespread symbols of wasteful legislative spending and prompted growing calls for a ban, especially from anti-tax conservatives. House Republicans and Senate Democrats have both prohibited the use of earmarks this session, but watchdog groups complain that some lawmakers continue to seek ways around the moratorium.

Fifteen years ago in the House, earmarks were growing in popularity but still controlled primarily by the 13 powerful appopriations chairmen, who often doled them out as favors to legislative or industry allies.

That changed after the May 1996 memo from Gingrich — called “Proposed Principles for Analyzing Each Appropriations Bill” — which advocated opening up the process to all GOP members. Records show a notable shift in who got earmarks during that time, as multimillion-dollar earmarks began showing up under the names of a growing number of Republican freshmen.

Steve Ellis, vice president for Taxpayers for Common Sense, which criticizes the use of earmarks, said Gingrich’s strategy proved to be a critical moment. “It was essentially the democratizing of earmarks,” Ellis said. “What Speaker Gingrich did was make earmarks available to the rank-and-file, not just the powerful appropriators. It opened the floodgates.”

Examples of earmarks from that time include $35 million for a veterans hospital, a university agriculture building and a dredging project for Rep. Frank Riggs (R-Calif.); $11 million for a deteriorating sea wall along Chicago’s Lake Shore Drive for Michael Patrick Flanagan (R-Ill.); and $8 million for a levee repair project for Randy Tate (R-Wash.).

Riggs, now head of a charter-schools lobbying group, defended the projects he earmarked in 1996. But he acknowledged that political campaigns sometimes played a role in why they were approved.

“The project had to be viable,” he said. “A secondary consideration was whether members were facing elections in very competitive districts. That did cause extra weight to be added to a request.”

Democrats also had many high-profile earmarks, although they tended to go to members with longer tenures. They included $21 million for a health clinic and barracks at Fort Bragg for Rep. W.G. “Bill” Hefner (D-N.C.); $10 million for military house for ranking member Robert C. Byrd (D-W.Va.) and $560,000 for security improvements at the El Paso Federal Building for Ronald Coleman (D-Tex.).

Before 2008, members of Congress did not have to disclose when they requested an earmark, making it impossible to tally a partisan breakdown.

Gingrich has turned sharply against the use of earmarks since leaving Congress, calling them a “gateway drug” to excess spending.

“These kinds of pork-barrel spending are abuses of power and abuses of the public trust — not to mention a waste of taxpayer dollars,” he wrote in a 2008 issue of Human Events, a conservative magazine. “They cannot be allowed to continue.”

Gingrich added: “No one has been tougher on the candidates and elected officials of both parties about changing the broken bureaucratic, special interest culture of Washington than I have been.”