(CNN) Bernie Sanders advocated for the nationalization of most major industries, including energy companies, factories, and banks, when he was a leading member of a self-described "radical political party" in the 1970s, a CNN KFile review of his record reveals.

Sanders' past views shed light on a formative period of his political career that could become relevant as he advances in the 2020 Democratic primary.

Many of the positions he held at the time are more extreme compared to the more tempered democratic socialism the Vermont senator espouses today and could provide fodder for moderate Democrats and Republicans looking to cast the Democratic presidential candidate and his beliefs as a fringe form of socialism that would be harmful to the country.

Aspects of Sanders' plans and time in the Liberty Union have been reported before, but the material taken together, including hundreds of newly digitalized newspapers and files from the Liberty Union Party archived at the University of Vermont, paint a fuller portrait of Sanders' views on state and public-controlled industry at the time.

In a statement to CNN, Sanders campaign spokesman Josh Orton said, "Throughout his career, Bernie has fought on the side of working people and against the influence of both the powerful ultra-rich and giant corporations who seek only to further their own greed. The record shows that from the very beginning, Bernie anticipated and worked to combat the rise of a billionaire ruling class and the exploding power of Wall Street and multinational corporations. Whether fighting to lower energy prices or expand access to capital for local development, Bernie's first priority has always been -- and will always be -- defending the interests of working people across the country."

After moving to Vermont in 1968 several years after graduating college, Sanders became an active member of the left-wing Liberty Union Party. Under the Liberty Union banner, Sanders, then in his early 30s, ran for governor of Vermont in 1972 and 1976 and as a candidate for US Senate in 1972 and 1974. Sanders, also served as chairman of the party from 1973-1975. During this time, Sanders and Liberty Union argued for nationalization of the energy industry, public ownership of banks, telephone, electric, and drug companies and of the major means of production such as factories and capital, as well as other proposals such as a 100% income tax on the highest income earners in America. Sanders also rejected political violence and criticized the anti-democratic nature of communist states such as the Soviet Union.

"I favor the public ownership of utilities, banks and major industries," Sanders said in one interview with the Burlington Free Press in 1976.

In his career as a US Senator, Sanders has backed away from such ardent calls for nationalization, but maintained similar rhetoric on wealth inequality. In one 2015 speech, he said he didn't want the government to take over private business or "own the means of production." But his early views are notable because they are far to the left of the current Democratic party and most candidates running for office.

Sanders left the Liberty Union Party in 1977 , over what he said was the party's lack of activity between elections. Sanders said in his farewell that workers would need to take control for the country to be sustained.

"The function of a radical political party is very simple," he said . "It is to create a situation in which the ordinary working people take what rightfully belongs to them. Nobody can predict the future of the workers' movement in this country or the state of Vermont. It is my opinion, however, that if workers do not take power in a reasonably short time this country will not have a future."

The energy industry

In 1973, during his time as chairman of the Liberty Union Party, Sanders took to a Vermont paper to oppose Richard Nixon's energy policy and oil industry profits, calling for the entire energy industry to be nationalized. Consumers at the time had been facing steep price increases and heavy shortages as a result of the OPEC oil embargo.

"I would also urge you to give serious thought about the eventual nationalization of these gigantic companies," Sanders wrote in a December 1973 open letter to Vermont Sen. Robert Stafford that ran in the Vermont Freeman. "It is extremely clear that these companies, owned by a handful of billionaires, have far too much power over the lives of Americans to be left in private hands. The oil industry, and the entire energy industry, should be owned by the public and used for the public good -- not for additional profits for billionaires."

Electric and telephone utilities

Efforts to push for public ownership of Vermont's utilities like telephone and electric companies played prominently in Sanders' political career in the 1970s. Sanders ran for Senate in a January 1972 in the special election and governor in that year's November election, registering in the low single digits in both races.

When he launched his first campaign for the Senate in 1971, Sanders said state utilities needed to be run by the state of Vermont on a nonprofit basis and that if revenues exceed expenditures they could be used to fund government programs and lower property taxes. In 1976, Sanders went even further: calling for the state to seize ownership of Vermont's private electric companies without compensation to investors. He defended his proposals routinely by pointing out that municipally owned utilities, not uncommon throughout the country, often had lower consumer prices.

Utilities like the Green Mountain Power company and the New England Telephone company had been steadily pushing, successful and unsuccessful at times, for approval from state regulators for rate increases. Sanders was particularly incensed by a proposed 27% rate hike by the New England Telephone company, and it became a rallying cry for his political campaigns.

In 1973, as chairman of the Liberty Union Party, Sanders had organized boycotts to stop proposed rate increases from New England Telephone company. Sanders' efforts through the "The Vermont Telephone Boycott Committee" -- a committee he coordinated that year -- proved successful in blocking NET rate increases. Newspapers commended Sanders for efforts when the rate increases were blocked by the state's utility regulators.

Sanders would declare for the Senate again the following June in 1974 and for governor in 1976, and Vermont's utilities would remain a major focus point of his campaigns and Liberty Union Party. Sanders' rhetoric was strongest during his 1976 campaign for governor of Vermont, his last before he left the Liberty Union Party.

In a press release on his policy positions, Sanders campaigned on the public ownership of the state's electric companies, without compensating the banks and stockholders.

"I will be campaigning in support of the Liberty Union utility proposal which calls for the public ownership of Vermont's private electric companies without compensation to the banks and wealthy stockholders who own the vast majority of stock in these companies," he said in a July 1976 press release . "I will also be calling for public ownership of the telephone company -- which is probably the single greatest rip-off company in America."

Sanders argued utility companies engaged in "economic blackmail," saying the state gave the companies the right to charge "outrageous" rates for utilities or have consumers suffer from poor service.

Sanders' comments went beyond the Liberty Union's proposal for public takeover of state utilities , which said investors and bondholders with more than 100 shares would have to convert their holding to non-voting stock and income bonds which carry no fixed claim to dividends or interest payments.

Public ownership of banks, corporations and the major industries

Sanders' policy proposals that year also included an ambitious plan to deal with companies attempting to leave towns.

"We have got to begin to deal with the fact that corporations do not have the god-given right to disrupt the lives of their workers or the economic foundation of their towns simply because they wish to move elsewhere to earn a higher rate of profit," Sanders said in a press release in August 1976.

Sanders' plan would require large businesses attempting to leave cities to get permission from the towns and the workers in them. If the company did not get that approval they would be required by law to pay a guaranteed two years of severance for workers and 10 years of taxes for the town.

Nationally, Sanders said, legislation corporations leaving cities would have to be dealt with by turning the means of production over to the workers.

"In the long run, the problem of the fleeing corporations must be dealt with on the national level by legislation which will bring about the public ownership of the major means of production and their conversion into worker-controlled enterprises," he said.

Campaign literature that year from Sanders, including a 1976 brochure for the party , said, "I believe that, in the long run, major industries in this state and nation should be publicly owned and controlled by the workers themselves."

Public control of the economy would become the key issue in his race. Speaking at one forum , Sanders called for workers to control of capital, factories, banks and corporations.

"There is a handful of people sitting at the head of the main banks controlling the destiny of underprivileged nations, the country as well as Vermont's economy," Sanders said . "That is not tolerable. That control cannot be held by them. We need public control over capital; and the capital must be put to use for public need not for the advancement of those who made the investments."

In an interview with the Burlington Free Press , Sanders argued the richest two or three percent should not control capital.

"I favor the public ownership of utilities, banks and major industries. In Vermont we have some $2 billion of deposits in our banks," Sanders told the paper. "In Vermont, as well as nationally, it is not tolerable to me that the control of capital would remain in the hands of the richest two or three percent of the population to do with it as they like."

Sanders called that year in a policy paper for Vermont's banking laws to be "radically" revised, so that the public and the state "determine in what manner our savings are invested so as to make Vermont a better place to live."

Socialized medicine and public ownership of drug companies

Asked about healthcare , Sanders said there would need to be publicly-controlled drug companies.

"I believe in socialized medicine, public ownership of the drug companies and placing doctors on salaries. The idea that millionaires can make money by selling poor people drugs that they desperately need for highly inflated prices disgusts me," he said.

Taxing assets at 100%

Heavy taxation of wealthy people played prominently into Sanders' plans to pay for expanding government services.

In February 1976, L iberty Union put out a state tax proposal calling for a radical revamping of the system, including the removal of all taxes of sales, beverages, cigarettes, polls, and the use of telephones, railroads or electric energy. Tax rates for those earning more than $100,00 would be 33.47%, $50,000-$99,999 would be 19%, $25,000-$49,000 would be 13.56%, and $10,000-$14,999 would be 4%. Anyone earning less than $10,000 would pay no state income tax.

But Sanders' rhetoric at times went much further.

During his 1974 Senate run, Sanders said one plan to expand government included making it illegal to gain more wealth than person could spend in a lifetime and have a 100% tax on incomes above this level. (Sanders defined this as $1 million dollars annually).