Senator Jesse Helms, member of the US Senate's foreign relations committee for two decades and its chairman from 1995 to 2001, has died at the age of 86. To echo this newspaper's memorable comment on the death of William Randolph Hearst, it is hard even now to think of him with charity. From his earliest years, Helms's attitudes recalled those of an earlier southern bigot, Theodore Bilbo of Mississippi, who so outraged his Senate colleagues, that they eventually refused even to let him take his seat.

There was never a comparable risk for Helms, who maintained an old-world courtesy in his personal contacts. But that was only on the surface. He became one of the most powerful and baleful influences on American foreign policy, repeatedly preventing his country paying its UN contributions, voting against virtually all arms control measures, opposing international aid programmes as "pouring money down foreign rat holes", and avidly supporting military juntas in Latin America and minority white regimes in Southern Africa.

In domestic politics he denounced the 1964 Civil Rights Act as "the single most dangerous piece of legislation ever introduced in the Congress", voted against a supreme court justice because she was "likely to uphold the homosexual agenda", acted for years as spokesman for the large tobacco companies, was reprimanded by the justice department and the federal election commission for electoral malpractice, and compiled a dismal personal record as a slum landlord.

The irony was that he was often seen as a relative moderate in his home state of North Carolina. His views sprang directly from his background as the son of the police chief in the small town of Monroe. Even before the Depression, life there was a constant struggle. It produced generations of deeply conservative poor whites, steeped in jingoistic patriotism and fundamentalist religion, who regarded the surrounding black population as barely part of the human race.

Helms was educated at local schools and had just enrolled for a college course when America entered the second world war. In 1942, he joined the navy, to be given a role which inadvertently established his postwar career. As a recruiting officer, he had to make regular patriotic appeals on local radio. They brought him sufficient recognition after the war to abandon his college studies for journalism, initially as news editor of the Raleigh Times and later as director of news and programmes for the principal local radio network.

In 1960, he was given an extraordinary boost when the owner of the main local television station appointed him one of the new medium's first editorial commentators. For 12 years, Helms appeared nightly at peak viewing time to denounce the civil rights struggle, trade unions, the UN, Lyndon Johnson's war on poverty, hippies, and any other social or political development rejected by the extreme right. His commentaries were repeated by 70 southern radio stations and, as they became increasingly popular, reprinted in 200 newspapers across America.

In a climate well to the right of mainstream politics in Europe, Helms became extraordinarily influential among those Americans Richard Nixon dubbed the silent majority. At the same time he built up a solid political network in North Carolina, working for several conservative senators, serving on Raleigh town council, running the state's bankers' association, and joining the Masons, their associates the Shriners, and the Rotarians.

By the time the Republican Richard Nixon moved into the White House in 1969, Helms's political ambitions had been focused. In 1972, in a state that had voted solidly Democratic since the civil war, he stood for the Senate as a Republican. In a bitter campaign against a middle-of-the-road opponent, Helms won by 8%. It was a signal of the South's seismic political shift after years of Democratic desegregation. It also made Helms the first North Carolina Republican to sit in the US senate for nearly 80 years.

His initial ambition was to secure his place on the agriculture committee, where he could push the interests of the powerful tobacco lobby for which he had worked for years. But, in a move which proved a stroke of near-genius at a time when direct-mail was in its infancy, he and two close associates organised a postal campaign for a body they named "the National Congressional Club". The repeated arrival of impressive-looking letters signed by Helms and denouncing school busing, funding for the arts, compensation for Japanese-Americans, the Red menace, and umpteen other liberal causes, sparked a stunning national response.

His allegations were often mind-numbingly bizarre. "Your tax dollars are being used," he claimed in one letter, "to pay for grade school classes that teach our children that cannibalism, wife-swapping, and the murder of infants and the elderly are acceptable behaviour." But his rhetoric convinced millions of Americans and, invited to save the nation by donating a dollar, they did just that. A river of cash poured into the club.

What happened to it all remained a constant mystery and, as the rules on election finances were slowly tightened, the club's accounts grew ever fuzzier. Some cash certainly went to the Coalition of Freedom, which had Helms as its honorary chairman until federal tax authorities began investigating its illegal campaign activities.

More than $800,000 went to a firm called Jefferson Marketing. Then the election commission established that this company was inseparable from the club, making its electoral operations unlawful. Less traceable were donations to other conservative groups and to fundamentalist religious figures like Jerry Falwell.

What is beyond question is the malign impact of Helms's innovation on all subsequent American politics. He inaugurated the age of massive back-door political donations, now euphemistically known as "soft money". In his own 1984 re-election battle, he spent $16.5m, then the most expensive Senate campaign in American history (and the federal election commission twice penalised him for using illegal contributions). Sixteen years later, a New Jersey candidate would lavish $60m on gaining a Senate seat, making it evident how effectively Helms's initiative had opened political office to the highest bidder.

It had also bankrolled the rise of the religious right and its effective takeover of the Republican party. That in turn polarised the entire American electorate, as the results in 2000 so dramatically demonstrated.

With Helms's agenda moving into the political mainstream — opposition to abortion, gun control, foreign entanglements, multicultralism, social welfare, educational reform and a host of other liberal policies — millions of voters dropped out and the rest divided evenly into mutually hostile camps.

For all his political posturing, however, Helms repeatedly showed himself inept at the tedious business of shepherding legislation through Congress.

The Senate's tradition of choosing committee chairmen by seniority eventually brought him to head the agriculture committee (1981-87). It should have been an enviable chance to promote North Carolina's farming and tobacco interests, which employ half its people. Yet the state, ranked eleventh by population, had one of the nation's highest poverty rates and lowest levels of federal funding.

Helms contributed his share to this misery with his ownership of rented houses in poor black districts of Raleigh. Some tenants reported that his properties had been without adequate heating for 30 years. The city's building inspectors repeatedly issued summonses against Helms to remedy a wide range of dilapidations, from rotting floors to leaking pipes.

Helms's principal skill, in fact, was obstruction, which he employed ruthlessly once he assumed chairmanship of the foreign relations committee in 1995, having been a member since 1981. The Senate's arcane rule book offers virtually uncontrollable power to committee chairmen to determine their own agenda. In a private war with the state department, Helms refused to hold confirmation hearings for 18 new ambassadors, or to debate such key issues for the Clinton administration as the chemical weapons or strategic arms treaties.

He cut the state department's funds by $1,700m until the administration finally agreed to his reorganization proposals, abolishing the arms control and information services and placing new restrictions on the US aid agency. In 1996, he caused an international furore by joining forces with Congressman Dan Burton of Indiana to push through the Helms-Burton Act, extending American jurisdiction to international companies trading with Cuba.

But continued Republican control of the Senate meant that Helms could not be ignored. He established a Jesse Helms Centre in his home town of Wingate, at which American and foreign dignitaries could pay homage. Those unable to attend in person could demonstrate their goodwill in cash: Taiwan donated $225,000, Kuwait $100,000, and various tobacco companies more than $1m.

Former president Jimmy Carter, secretary of state Madeleine Albright, Dr Henry Kissinger, the chairman of the joint chiefs of staff, and other key public figures all turned up. Eventually even the UN secretary general, Kofi Annan, heeded the call: in the aftermath of his visit, the foreign relations committee suddenly released America's long-outstanding payments to the UN.

In later years, Helms suffered from increasingly poor health. He contracted prostate cancer and a bone disorder, Paget's disease, which obliged him to travel round the Senate building on a scooter. He also underwent a quadruple heart bypass.

Helms finally lost his chairmanship of the foreign relations committee when the moderate Vermont Republican Senator James Jeffords, lost patience with the Bush administration in May 2001. His defection to the Democrats secured their control of the Senate and of all its legislative committees.

This sudden loss of power, allied to his failing health, at last convinced Helms that it was time to give up. In August that year, he announced he would not run again when his term expired in 2002.

Though there was dismay in North Carolina, his decision was greeted with relief by most of the country. The New York Times observed: "Few senators in the modern era have done more to resist the tide of progress," and Robert Pastor, whose ambassadorship to Panama was scuppered by Helms in 1995, commented that, "nothing Jesse Helms did in his entire career will enhance America's national security more than his retirement."

He is survived by his wife Dorothy, two daughters and a son.

 Jesse Helms, politician, born October 18 1921; died July 4 2008