The latest Republican effort to repeal the Affordable Care Act is in deep trouble. As in July, when the previous repeal effort faltered, Maine Sen. Susan Collins seems likely to be one of the Republicans who splits with her party and kills it once and for all. (Yesterday, she declared that it would be very difficult to envision a scenario under which she voted for the bill.)

Her stubborn refusal to support two vehicles for achieving her party’s top legislative priority has exemplified Collins’s independent streak. During her Senate career (1997-2015), Collins has voted with her party about 60 percent of the time. During that period, only five senators voted with their party less, none of whom remain in the Senate.

While other Republicans, like Sen. John McCain (R-Ariz.), garner more attention when they buck the party, Collins is the last true heir to the moderate Republican lineage in the Senate.

In asserting her independence, Collins builds upon the legacy of Maine’s first maverick female senator, Margaret Chase Smith — who spent two hours inspiring a teenage Collins on a visit to Washington. Long a thorn in the side of the Republican establishment because of her support for pro-internationalist and pro-labor policies, Smith is best known for her famous 1950 speech excoriating Sen. Joseph McCarthy (R-Wis.) for his red baiting.

Yet, this “Declaration of Conscience” actually damaged Smith’s career more than McCarthy’s, exposing the deep sexism that pervades congressional politics. Collins and her fellow female Senate maverick, Lisa Murkowski (R-Alaska), however, have something that Smith did not have: a vocal  grass-roots women’s movement that is essential to surviving the blowback from angry conservatives.

First elected to the House of Representatives in 1940, Smith ascended to the Senate in 1948. As the first woman to make the transition, she quickly became the darling of the liberal Republican establishment. They hoped that the novelty of her victory would attract women and blue-collar voters to the party, still smarting from repeated electoral setbacks at the hands of FDR. Liberals also hoped that Smith’s popularity would facilitate their takeover of the party leadership.

The perception of Smith as party savior was short-lived. Within a few months, she became estranged from liberal congressional Republicans because of her discomfort with McCarthy’s rise.

Although Smith shared McCarthy’s staunch anti-Communism, she found his penchant for lying to colleagues and chasing publicity disquieting. His accusations that Communists had infiltrated the government troubled Smith, because they were riddled with factual inconsistencies. She pointedly noted the ever-shifting numbers of alleged Communists in McCarthy’s screeds and demanded to see the material upon which his accusations were based. What he provided failed to clarify the magnitude of the possible infiltration.

In an atmosphere permeated by fear, several prominent journalists noted Smith’s discomfit and encouraged her to denounce McCarthy’s tactics of character assassination and guilt by association. Her reputation for independence and propriety made her the perfect person to do it. Her gender also helped. Throughout her career, Smith had evoked the long-standing stereotype (which dated to the first wave of the women’s movement in the 19th century) of women as a force for civility and decency in the public arena who balanced the male tendency for graft and immorality.

Smith heeded the journalists’s pleas and on June 1, 1950, she took to the Senate floor to deliver her denunciation of McCarthy. Titled the Declaration of Conscience, the brief speech set out a list of basic Republican principles and called on the Senate to recommit itself to freedom of speech and freedom of independent thought.

Editorial reaction to the speech was sharp and swift. Much of it focused on the relationship between gender and public morality. Newsweek put Smith on the cover and noted that her “precise, restrained phrases worked as neatly as a broom sweeping out a mess.” By contrast, the Chicago Daily Tribune trashed Smith in gendered terms, referring to the declaration as “the recent breast beating act put on by Senator Smith” and accused the Truman administration of seducing Smith with a “subsequent gracious appointment” to attend a UNESCO conference in Italy.

Smith’s mail on this speech ran eight to one in support of her position, providing a measure of vindication. Yet, despite this popular support, the Declaration of Conscience marked the end of Smith’s crusade against McCarthy. She took no concrete action against him. In fact, she never even mentioned McCarthy again by name and later left the subcommittee considering his Senate expulsion.

Political isolation guided Smith’s decision to stand down. Not only was she the only female senator, but Smith was also a junior senator who had attacked a more senior colleague in an institution governed by seniority — which didn’t endear her to her peers. Intimidated by the possibility of conservative retaliation, Smith’s ideological allies had also beat a hasty retreat.

Additionally, her tiny state gave Smith little political clout, and thanks to her ideology, she was estranged from significant political elements back home — a predicament long exacerbated by her unwillingness to follow custom and step aside for a male successor after she replaced her late husband, congressman Clyde Smith.

Smith’s gender also contributed to her precarious political predicament in another way. With the splintering of the woman’s movement that fought for suffrage in the early 20th century, Smith’s cultivated persona, which played up her moral superiority, had declined in political utility. In the world of the 1950s, women belonged at home, not in electoral politics scolding a male colleague.

To avoid the demeaning and politically counterproductive caricature of a carping school marm excoriating unruly men, Smith blunted her criticism of McCarthy. There were already enough reminders that she did not fit the stereotype of a senator.

While the Declaration of Conscience ultimately contributed little to the downfall of Sen. McCarthy, Smith always believed that it thwarted her career and diminished her standing among her colleagues by creating the impression that she was difficult and idiosyncratic.

But today, female politicians confront a different landscape. Being vocal and independent is not something they do alone, as decades of activism has resulted in a well-organized grass-roots movement to back Smith’s successors like Collins. Smith’s career suffered not because of the substance of the Declaration of Conscience but because of her gender. As the only woman in the Senate, the speech no one wanted to hear could easily be dismissed as whiny, carping and even bitchy. With no female colleagues and no grass-roots women’s movement demanding that Smith be taken seriously, she was easily disregarded.

Currently there are 21 women in the Senate. Their presence is a critical mass that redefines what a senator looks like and cares about. Yet, ours is also a period in which efforts to delegitimize women in politics occur almost daily. This reality makes grass-roots action from organizations such as the Women’s March on Washington critically important for insuring that women are not marginalized and defined once again as second-class citizens. Even when these grass-roots organizations disagree with Collins’s policy prescriptions, they will support her right to express them, especially when she is isolated from fellow Republicans and might otherwise languish on a lonely political island as Smith did.