Nearly two years ago, Raphael Warnock and Jon Ossoff won runoff elections in Georgia that allowed the new vice president, Kamala Harris, to be the Senate’s tiebreaking vote. Those victories were critical to unleashing a remarkable wave of legislation and spending.Without Mr. Warnock and Mr. Ossoff, President Biden could not have made substantial investments in roads, bridges, public transportation and semiconductor chip manufacturing. He could not have permitted Medicare to negotiate the price of prescription drugs. He could not have taken tangible steps to combat climate change. The 2021 tranche of federal pandemic aid, today criticized for contributing to inflation, offered critical bailouts for local governments that headed off crippling layoffs and brutal cuts to public schools.Now Mr. Warnock is locked in another runoff on Dec. 6, this time against Herschel Walker, the former football star. The stakes feel lower for this one: Democrats are already guaranteed a Senate majority. And no matter the outcome in Georgia, Congress will be divided, with the House in the hands of Republicans.Yet the outcome of Mr. Warnock’s contest matters significantly, for Democrats and Republicans alike — but especially for Democrats. They need Mr. Warnock in power for at least two overriding reasons: to safeguard their gains in the judiciary and to bolster their national bench.Under President Donald Trump, Mitch McConnell was venerated — or denounced — for his efficient and cutthroat approach to ramming through Mr. Trump’s Supreme Court picks and confirming federal judges.In four years, Mr. McConnell’s Senate majority confirmed three right-wing justices and 234 new judges overall, many of them youthful conservatives rubber-stamped by the Federalist Society. These Trump appointees can serve for the rest of their lives; it is plausible that some of them will still be remaking federal law 30 or 40 years from now. Most of these judges are avowed originalists, fiercely opposed to the “living Constitution” school that dominates liberal jurisprudence and allowed for all sorts of social progress that is now being turned back. The overturning of Roe v. Wade is the exemplar.Since Democrats retook the Senate majority in 2021, Mr. Biden has undertaken his own successful counteroffensive, in tandem with Chuck Schumer, the Senate majority leader. Mr. Schumer’s Senate has actually confirmed federal judges at a faster rate than Mr. McConnell’s at the time of the first midterm election. So far, over 85 judges appointed by Mr. Biden have been confirmed, including a new Supreme Court justice, Ketanji Brown Jackson. The judges, overall, are traditional liberals, many of them younger and nonwhite. Mr. Biden and Mr. Schumer were willing to elevate judges who were former public defenders, an unlikely prospect in the law-and-order 20th century.If Mr. Warnock wins, the Senate can move more rapidly and seek judges who are perhaps more progressive in their worldviews — the sort who could hit a snag if someone like Joe Manchin, the centrist from West Virginia, or Kyrsten Sinema of Arizona is the deciding vote.Democrats must evenly split committee members in the 50-50 Senate, giving Republicans the power to delay votes on judges. A 51-49 majority would be much more dominant: Committees like the judiciary would be stacked with Democrats, greatly speeding up the confirmation process. There are about 75 vacancies on U.S. District Courts and nine at the appellate level. That number is bound to grow as more judges retire in the next two years.Democrats, with Mr. Warnock, could also be in position to replace a Supreme Court justice. The 6-3 conservative majority makes this seem less pressing, but Ruth Bader Ginsburg’s death was a lesson that Stephen Breyer, who retired this year, seemed to heed: Once you’re of retirement age, it’s best to leave the court if an ideologically friendly president and Senate majority are in control.Sonia Sotomayor is 68 and Elena Kagan is 62. Both can serve for decades, but Democrats have to think seriously about the practical advantage of installing liberal justices who are in their 40s or early 50s. Amy Coney Barrett was confirmed at 48; Neil Gorsuch was 49. Justice Breyer wisely gave way to Justice Jackson. Perhaps Justice Sotomayor, at least, should give thought to stepping aside with Mr. Biden in the White House and Mr. Schumer guiding the Senate. With 51 votes, Mr. Schumer could steer through a judge who is as progressive as either Justice Sotomayor or Kagan, helping to nurture a liberal minority that could theoretically expand someday.And then there’s 2024. If Mr. Walker defeats Mr. Warnock, Republicans will have an enormous advantage in their quest to not only flip the Senate but also build a durable majority that could last a generation or more. The 2024 map is foreboding for Democrats: Assuming they run for re-election, three incumbents represent states that Mr. Trump handily carried in 2020. Mr. Manchin, resented by the left, will have to find a way to win in deep-red West Virginia (Mr. Trump carried the state in 2020 with nearly 70 percent of the vote). Senator Sherrod Brown of Ohio (who has stated he will run) will have to win a state that has now twice voted for Mr. Trump and is sending J.D. Vance to Washington. Jon Tester of Montana has the daunting task of trying to win a rural state that has in recent years become inhospitable to Democrats for statewide offices.A 51-49 majority is a better hedge against such a possible wipeout. It also gives Mr. Warnock a chance to shine on the national level and demonstrate whether he can become a formidable member of an expanding Democratic bench, the kind of senator who could end up president someday.It’s tantalizing to consider whether the Georgia senator holds answers to the various major and minor crises looming over the future of the party. Mr. Warnock, like Barack Obama, is a Black politician who has proved he can weave together multiracial coalitions, retaining working-class support in communities of color while attracting some right-leaning voters and independents, many of them white. To finish just ahead of Mr. Walker in November, Mr. Warnock had to win over a sizable number of Georgians who were voting to re-elect the Republican governor, Brian Kemp. Mr. Warnock boasted repeatedly of his bipartisan bona fides — his campaign is still actively courting Kemp voters, even as the governor stumps for Mr. Walker — while retaining enthusiasm from the Democratic base. He did this in part by being a reliable supporter of the Biden policy agenda in Washington, avoiding the posture of needless antagonism that made both Mr. Manchin and Ms. Sinema enemies of the left for much of the past two years.Mr. Warnock enters the final stretch with three times as much cash on hand as Mr. Walker, who is lately trying to fend off a deluge of negative TV ads and allegations of carpetbagging. Once more, America’s fate is bound up in Georgia, and Mr. Warnock’s own political star may yet shine much brighter in the weeks to come.Ross Barkan, a novelist, is a contributor to New York Magazine and The Nation.The Times is committed to publishing a diversity of letters to the editor. We’d like to hear what you think about this or any of our articles. Here are some tips. And here’s our email: letters@nytimes.com.Follow The New York Times Opinion section on Facebook, Twitter (@NYTopinion) and Instagram. More