Labor advocates and critics alike can debate the reasons for the decline of union membership in America over the last seven decades, but one event gets the nod from both sides as a major obstacle to union organizing.

It’s the passage in 1947 of the Taft-Hartley Act.

“Taft-Hartley was devastating to labor,” the former (and reformed) union-buster Martin Jay Levitt wrote in 1993. In labor relations, he observed, management always had the upper hand. But after Taft-Hartley, “the bosses could once again wage their war with near impunity.”

So it’s understandable that the two most progressive candidates running for the Democratic nomination for president, Sens. Bernie Sanders and Elizabeth Warren, have called for repeal of sections of the act.

But have they gone far enough? Veteran union strategist Rich Yeselson thinks not. Instead of piecemeal revision or repeal of some provisions of Taft-Hartley, he says, “why not just shoot the moon: Get rid of this awful law!”

Taft-Hartley was the product of three threads in American politics of the late ’40s that became braided together. One was the red scare, which became directed at unions such as the CIO that had relied on communist organizers to do unionizing work on factory floors.

Another was the burgeoning influence of corporate managements, especially after Republicans took over the House and Senate in 1946, the first time the party controlled both chambers of Congress in 18 years.

The third was a public backlash to a wave of postwar strikes, including a general strike in Oakland in December 1946. The Oakland strike was an “almost unprecedented demonstration of worker power,” labor historian Erik Loomis has written.

But it also raised the hackles of voters in regions where union representation was not strong — such as outside the industrial heartland and Northeast. An estimated 14 percent of all workers had participated in postwar strikes, which made the wave of labor unrest appear to be virtually universal.

Even liberal Democrats weren’t above riding the anti-union wave. One was Lyndon Johnson, who attacked Coke Stevenson, his opponent in his 1948 campaign for the Senate, for being beholden to unions — while he himself “courted CIO support behind the scenes,” Loomis noted.

Harry Truman vetoed the Taft-Hartley Act, but as a Democratic president he was outgunned. Congress overrode his veto with large margins, and the fate of the union movement was sealed.

It’s certainly true that union leaders deserve some of the blame for the long-term decline of organized labor, as do fundamental changes in the nature of work and employment in the U.S. over the last 70 years. But Taft-Hartley set the groundwork for that decline in myriad ways.

After Ronald Reagan scored his victory over the Professional Air Traffic Controllers Organization, or PATCO, by firing its striking members in 1981, employers followed his lead by instituting an era of unexampled hostility to organized labor. Taft-Hartley provided them with the playbook.

The best-known provision of Taft-Hartley may be the infamous section 14(b), which allows states to enact “right-to-work” laws that prohibit contracts requiring union membership as a condition of employment. Right-to-work laws have been enthusiastically embraced by 27 states, including the entire Southeast.

The spread of right-to-work laws led to the emergence of the free-rider problem, in which nonunion members benefit greatly from union contract negotiations and enforcement of contract provisions, but don’t have to pay dues to support that work. The National Right to Work Committee, a leading promoter of these laws, has ties to the Koch network, though it describes itself as “a coalition of 2.8 million workers, small business owners and freedom-loving Americans.”

Other provisions of Taft-Hartley are equally damaging to unionization efforts. It prohibited mass picketing, sit-down strikes and secondary boycotts, in which unions take aim at suppliers or customers of their primary target.

The law also tightened the definition of “supervisor,” removing the eligibility for unionization from a sizable and influential cadre of workers. “Corporate managers and their allies in Congress viewed an alliance of unionized workers with unionized supervisors as . a grave challenge,” Yeselson observes. Taft-Hartley nullifed the challenge. The law also defined independent contractors as non-employees and therefore ineligible to join unions, setting up a conflict that has mushroomed into the gig-worker vs. employees controversies of today.

Sanders and Warren, to be fair, have turned their sights on repealing the most noxious provisions of Taft-Hartley.

Both are in favor of restoring the card check process. Both favor outlawing right-to-work laws and “captive audience” meetings staged by management. They endorse restoring the right to secondary boycotts, although as Yeselson reports, the prohibition in Taft-Hartley is murky enough to have allowed at least some union activities that might be considered to fall within the definition.

Both also call for addressing the Taft-Hartley restriction on unionization of supervisors, although Yeselson criticizes Warren for merely advocating a limitation on the definition, a step he argues would perpetuate battles over who is or isn’t a supervisor that complicates organizing efforts.

But both candidates arguably have missed a bet by focusing on these provisions as though they exist in individual silos, rather than being part and parcel of the most far-reaching attack on unions ever staged by Congress.

Michael Hiltzikis a columnist and reporter for the Los Angeles Times.