On June 1, 1950, the junior U.S. senator from Maine — a Republican and a woman — rose to her feet to challenge her party. Only the seventh woman ever elected to the male-dominated U.S. Senate, she had been in office for just over a year. To speak at all, let alone question her party, was to violate the tradition-bound Senate’s well-known disapproval of freshman speaking.

In laconic Maine style, her speech was brief and direct. She was speaking as a proud Republican who was sick of the “present ineffective Democratic administration,” but she couldn’t see how it profited her party to win the next election if in the process it lost its soul. She wanted the Republicans to win, she said, but “I do not want to see the Republican Party win that way. While it might be a fleeting victory for the Republican Party, it would be a lasting defeat for the American people.”

The speech resounded in the chamber, and for a brief moment — in what would come to be known as her “ Declaration of Conscience” — U.S. Sen. Margaret Chase Smith recalled the party of Lincoln. Afterward, the financier and statesman Bernard Baruch was heard to say that, if the speech had been made by a man, “ he would be the next President.”

This was not the last time the lady from Maine would put country before party.

Furious at the Senate’s rejection of his initial U.S. Supreme Court nominee, Clement Haynsworth in the spring of 1970, Nixon retaliated by nominating G. Harrold Carswell in his place. Legal scholars thought Carswell unfit on jurisprudential grounds, and his segregationist views and false testimony concerning those views during his confirmation hearing inflamed public opinion.

Yet despite the public outrage, Beltway insiders were confident he would be confirmed. And he nearly was. It was so close that the vice president’s tie-breaking vote might have been needed for Senate confirmation.

Despite the public show of party solidarity, and away from the klieg lights and the cameras, many rank-and-file Republicans knew Carswell was a catastrophic choice. The fault lines between the Republican president’s public policy and his party’s private conscience were felt but never discussed.

Smith was by now an elder stateswoman, but it took no less courage to withstand the marked pressure and vote against her party’s nominee for the highest court in the land. And yet, she voted “ no.” Her vote broke that silence, and in the wake of her vote, several senators who privately promised Nixon an “aye” vote, chose instead to follow her lead. The spell had been broken and Carswell was defeated. He would later be disgraced for separate, personal reasons.

Like Smith, U.S. Sen. Susan Collins is confronted with an executive in her party who is actively working to undermine core American values. Like Smith, Collins has a choice. She can contribute to another dark page in America’s history. Or she can carry on Maine’s proud tradition and bring light where it shines most brightly: in the darkest of night and in the defiance of her friends.

President Donald Trump made it clear on the campaign trail that he would seek a Supreme Court nominee who will overturn Roe v. Wade. If Judge Neil Gorsuch is confirmed for the Supreme Court, erosions of voting rights could become more pronounced. With the Supreme Court in the balance, the vote on Gorsuch is unprecedented in its magnitude for the rights of women, LGBT and people of color — all constituencies that have supported Collins’ career. America deserves an independent thinker, capable of standing up for the U.S. Constitution, even in defiance of a president if necessary.

As I can personally attest, standing up to one’s party does not win many friends. But America wasn’t built on political parties. It was built on courage — the kind of courage that stops a bad Supreme Court nomination.

Diane Russell served eight years in the Maine House of Representatives. She lives in Portland. Follow her on Twitter: @MissWrite.