As the field of early Democratic contenders for the 2020 presidential elections takes shape, debates over the party’s direction have become hotly contested. Will it move to the center to appeal to moderates or shift to the left to give voice to grass-roots populists? Establishment figures are already cautioning against progressive challenges, arguing that Democrats should focus instead on reasonable, moderate and coalition-building centrism to defeat Trump in 2020 and advance the party’s legislative agenda.

But the history of progressivism tells a different story. Much like today’s centrists, members of the political establishment during the Progressive Era also resisted calls for sweeping change. Referring to reform as “babble” and the movement as “largely meaningless and transient,” figures such as long-term congressman and two-time House speaker Joseph G. Cannon, a Republican from Illinois known as “Uncle Joe,” dismissed the progressive impulse as “hysteria and rash experiment.”

Obstructionists such as Cannon, however, were not the biggest problem. Rather, it was the politicians who co-opted the progressive agenda for political expediency, often diluting its intended effects.

Ideas about leveling economic and social inequalities animated progressive reformers around the turn of the 20th century, as they do their political descendants today. Beginning at the local and state level, progressive reformers pursued causes and policies that sought to address an array of issues, including worker protections, women’s rights, education, public health, conservation, welfare, representative government and the overall inequality wrought by industrial capitalism.

Reformers sought to tackle these issues with a more active and regulatory federal government. And while these progressive movements produced a plethora of reforms during the first two decades of the 20th century, their efforts did not resolve the deeper underlying issues of social and economic inequality. In fact, economic inequality intensified during the first quarter of the 20th century.

World War I and the ensuing period of resurgent laissez-faire pro-business policies upended most of this progressive wave. But so, too, did reformers who claimed the progressive label but were fundamentally conservative.

Consider, for example, Theodore Roosevelt, perhaps the most widely known “reformer” of the era. Working closely with some of the more obstructionist forces in Congress, such as Cannon and Senator Nelson W. Aldrich (R-R.I.), Roosevelt considered their conservative wing of the Republican Party to be the dominant faction in Congress. And so he consulted with them, deferred to them and yielded to them on many occasions.

On the issue of railroad rate regulation, for instance, Roosevelt opted for expediency over real reform proposals, such as those from Sen. Robert M. La Follette (R-Wis.), whom Roosevelt regarded as a demagogue. Roosevelt threw his weight behind the Hepburn Act, which helped railroad corporations much more than it helped consumers. In 1913, La Follette remarked that the law was “little more than a sham,” because “railroad rates steadily increased” and “[h]undreds of millions of dollars have been wrongfully taken from the American people.”

Roosevelt’s willingness to compromise on much of the legislation that reformers proposed partially explains his relatively few landmark accomplishments as president. Notwithstanding his conservation program or the Pure Food and Drug Act, Roosevelt’s reputation as a progressive icon largely stems from the time after his presidency, and especially from the election of 1912, when he advanced a rhetoric of reform.

By the spring of 1912, Roosevelt was looking for a way back into the White House, so he co-opted much of La Follette’s reformist platform and language to win over the progressive wing of the party. When the Republican establishment nominated incumbent William Howard Taft, Roosevelt bolted the GOP and quickly founded the Bull Moose Party with the help of wealthy friends who facilitated and bankrolled its infrastructure and operations. Then he doubled down on the progressive agenda, boldly championing policies such as direct primaries, direct election of senators, women’s suffrage, a federal income tax, infrastructural improvements, abolition of child labor, and stronger antitrust and labor laws.

One major obstacle to this agenda was that the Bull Moose Party, which hinged on the cult of personality around Roosevelt, remained a racially exclusive and largely white middle- and upper-class affair, one that relied on big money and political insiders.

Rather than bolstering the progressive movement, therefore, Roosevelt divided it. Although he launched the most successful third-party candidacy in history, with the progressive vote dispersed among Democratic challenger Woodrow Wilson and Socialist candidate Eugene V. Debs, Roosevelt came up short. As the war in Europe hampered American progressivism at home, Roosevelt once again deferred to conservative impulses. He reconciled and realigned with the Republican establishment by 1916, which reflected his earlier attitudes of compromise, deferment and incremental progress.

Today, the phenomenon of co-opting a progressive agenda can be seen in the growing support for Medicare-for-all among mainline Democrats. This idea is tremendously popular with the American public by some measures, but the specifics of the concept are not clearly defined. While most leftists and progressives tend to favor a universal single-payer health-care system like that of Canada or the United Kingdom, most establishment Democrats avoid the term “single-payer,” either by choice or because party operatives have advised them to do so.

Some 2020 hopefuls among the Democratic establishment, who had signaled support for Medicare-for-all, have recently wavered. Others who claim to have embraced it often merely talk about strengthening the Affordable Care Act or expanding Medicare with a public option (the idea behind Medicare X). Neither of these policies would seriously challenge the stranglehold that big insurance and big pharma have on the grossly unequal and commodified American for-profit health-care system.

Taking a page from Bob La Follette, today’s progressives should resist diluting their policies and accepting half loaves. More importantly, they should remain cautious of concerted attempts to co-opt their messages and momentum. Establishment Democrats may proclaim support for progressive causes, but there should be healthy skepticism as to whether they will actually deliver on those promises. As progressives pursue their goals and policies at the state and federal level, they should be wary of liberal-centrist attempts to adopt their agendas for disingenuous political expediency or watered-down compromises.