Jeffrey Bell attends a campaign event in Morristown, N.J., in 2014. (Mel Evans/AP)

Jeffrey L. Bell, a conservative intellectual who revealed voter appetite for lower taxes when he ousted a more liberal Republican, four-term U.S. Sen. Clifford P. Case (N.J.), in the 1978 primary, and who later became known as an early architect of Reaganomics, died Feb. 10 in Fairfax County, Va. He was 74.

The cause was cardiac arrest, said his wife, Rosalie O’Connell.

Mr. Bell’s political career was bookended by erudite and intriguing, if ultimately unsuccessful, bids for the Senate.

He ran his first campaign at age 34 against Case, who had served on Capitol Hill for nearly as long as Mr. Bell had been alive, first in the House of Representatives and since 1955 in the Senate. Mr. Bell went on to lose in the general election to former NBA star Bill Bradley, who sought the Democratic nomination for president in 2000.

At age 70, Mr. Bell again received the Republican nomination for Senate in New Jersey. His Democratic opponent in 2014 was Sen. Cory Booker, the former Newark mayor who had won a special election for the seat left vacant by the death of Sen. Frank R. Lautenberg (D).

Mr. Bell, right, with New Jersey Gov. Chris Christie during a 2014 campaign event in Morristown, N.J. (Mel Evans/AP)

Mr. Bell was remembered not for his losses at the polling booth but rather for the issues he brought to the campaign trail — chiefly, the conviction that Americans needed and deserved vastly lower taxes. He also promoted a monetary policy based on the gold standard, in which the value of money is linked to the value of gold, and supported conservative positions on social issues including abortion, proposing that fetuses receive the due process protections enumerated in the 14th Amendment.

His “populist insight,” observed Robert W. Merry, editor of the American Conservative, in a commentary after Mr. Bell’s death, was “that ordinary people are perfectly capable of making sound decisions on how to run their lives and didn’t need — and generally didn’t want — government bureaucrats and political elites co-opting those decisions.”

Mr. Bell was a speechwriter for Richard M. Nixon in 1968, the year Nixon defeated Democrat Hubert Humphrey to win the presidency, and for Ronald Reagan in 1976, when Reagan lost the primary to the incumbent Republican, Gerald R. Ford, but laid the groundwork for his landslide victory over Democratic President Jimmy Carter in 1980.

Outside politics, Mr. Bell served at times as political director of the American Conservative Union, president of the right-leaning Manhattan Institute and policy director at the American Principles Project, a conservative think tank he co-founded.

But he attracted perhaps greatest attention with his 1978 Senate run — by “moving up to New Jersey as a nobody,” Merry wrote, “and turning himself into a very effective, but always a very congenial, political giant-slayer.”

Mr. Bell ran chiefly on a platform of lowering taxes, including cutting the personal income tax rate by 30 percent.

“My reading of history is that radical changes take place very quickly. The French Revolution, the New Deal, the major civil rights acts of the 1960s all came quickly after pressure had built up over a long period,” he said during the campaign. “I sense a movement building in this country . . . We are at the end of a long period of frustration.”

Mr. Bell defeated Case by 3,473 votes out of 233,637 cast . Bradley proved a more formidable opponent and defeated him 55 percent to 43 percent.

Two years later, Mr. Bell again worked on Reagan’s presidential campaign. When Reagan won, Mr. Bell continued pressing for the tax cuts that became the basis of Reaganomics, a form of supply-side economic policy that promoted lower taxes as the most effective way of encouraging economic growth.

“If he had cashed out of movement politics in 1980, Jeff’s legacy would have been set. Instead he stayed on the insurgency,” Rich Danker, a former campaign manager and aide, wrote in the Weekly Standard magazine after Mr. Bell’s death. “He spearheaded a shadow cabinet and worked with the Democratic senator who defeated him in the 1978 general election — Bill Bradley — on the tax reform of 1986.”

That landmark act, one of the largest overhauls ever of the tax system, simplified the tax code and reduced rates.

In his race against Booker, Mr. Bell championed the gold standard, as he had done in 1982, when he lost a Senate primary to four-term Rep. Millicent Fenwick (N.J.) — like Case, a more liberal Republican. Fenwick lost that year to Lautenberg.

Reverting to the gold standard was an unconventional platform and one that gained little traction, but one in which Mr. Bell ardently believed.

“I just couldn’t get members of Congress and presidential candidates to take on the issue of monetary reform. So, rather suddenly,” he told the publication New Jersey Business, “I decided to come back and do it myself.”

Mr. Bell lost to Booker 56 percent to 42 percent.

Jeffrey Langley Bell was born in Washington on Dec. 13, 1943. His father was an executive with the DuPont chemical company, which took the family to Geneva during Mr. Bell’s high school years, and his mother ran a shelter for victims of domestic violence.

Mr. Bell received a bachelor’s degree in English literature from Columbia University in 1965 and served with the Army in Vietnam as an intelligence adviser.

In the late 1980s and through the 1990s, he was president of the consulting firm Lehrman Bell Mueller Cannon.

He was the author of two books, “Populism and Elitism: Politics in the Age of Equality” (1992) and “The Case for Polarized Politics: Why America Needs Social Conservatism” (2012).

Survivors include his wife of 34 years, Rosalie O’Connell of Annandale, Va.; four children, James Bell of Irving, Tex., Nicholas Bell of Annandale, Damian Bell of Austin and Julia Slingsby of Alexandria, Va.; a sister; and four grandchildren.