Opinion editor's note: Editorials represent the opinions of the Star Tribune Editorial Board, which operates independently from the newsroom.

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A critical though unsung test of leadership comes when it's time to exit the public stage, with the ideal leave-taking done at the right time, accompanied by grace and selflessness.

While President Joe Biden's troubling debate performance strongly suggested that he should have stepped aside sooner, his decision to do so now nevertheless exemplifies the latter two qualities. On Sunday, Biden, 81, announced that he will not run for re-election. It's a decision that certainly couldn't have come easily but one that prioritizes the nation's needs over his own.

Biden has ably served his country, with the strong economy in particular reflecting well on his stewardship. Among other accomplishments: the bipartisan infrastructure deal; passage of the CHIPS and Science Act, which will strengthen U.S. leadership in technology research and manufacturing, and the protections his administration has put in place for Minnesota's beloved Boundary Waters Canoe Area Wilderness. He also merits praise for his commitment to reproductive health freedom after the U.S. Supreme Court overturned Roe v. Wade in 2022.

The wisdom that comes with Biden's age was sorely needed after the COVID-19 pandemic and the exhausting chaos of former President Donald Trump's time in the White House. But the challenges ahead — domestic and foreign — are complex. There can be no doubts about the stamina of the nation's next CEO.

Biden assuaged some of these concerns in follow-up interviews and speeches after the disastrous debate in late June. But he couldn't erase all of them. Those who watched the debate were painfully reminded of watching their own aged loved ones become frail and fragile. Another four years of the world's toughest job just didn't seem realistic. Voters should apply that same hardheaded assessment to Trump, who is 78, and is known to fall asleep in the courtroom, forget names, mangle words in speeches and expound at length on head-scratching topics like sharks and electrocution.

With just three and a half months before Election Day, Biden regrettably leaves his party with scant time to designate a successor and re-engineer a campaign for the White House. It's a daunting undertaking, and the party should be given room to determine its best course of action. A challenge like this can be the crucible in which the next generation of Democratic Party leaders is forged. Hopefully, they'll rise to the occasion at the party's national convention in Chicago on Aug. 19-22.

Minnesota Gov. Tim Walz increasingly has had a high-profile role, becoming one of Biden's leading defenders in recent media appearances. The Star Tribune Editorial Board hopes that party leadership role continues after Biden's exit. Walz is an energetic voice not just for Minnesota, but for the Midwest, a region where Democrats have lost precipitous amounts of political ground in the past decade. The party should tap his expertise on issues important to the region as it hones its pitch to voters in months ahead.

Biden's decision is also an important opportunity for voters during the 2024 campaign. With capacity concerns about him now moot, Americans can and should focus more deeply on the policy differences between the two political parties. They're significant.

The Republican National Convention, which was held in Milwaukee and concluded July 18, put a disturbing spotlight on immigration. Signs displayed there called for "Mass Deportation Now!" While there are valid border security concerns, this supposed solution ignores this reality: that immigrants are a crucial part of the workforce in agriculture, meatpacking, construction and other industries. We're already in the midst of a historic labor shortage, and mass deportations would only exacerbate it. Basic humanity should also have a role in the nation's immigration policy, with this quality not readily apparent in Republicans' deportation sloganeering.

Other key policy differences:

• Ukraine. Trump's new running mate, Ohio Sen. JD Vance, is among the leading congressional opponents of Ukrainian aid. Biden's foreign policy, one his successor likely would continue, has forged international support for Ukraine and kept munitions flowing to it. While Trump's allies have recently touted his ability to broker a peace deal in the conflict, voters should question whether that "peace" involves rewarding Russia's aggression with Ukrainian territory, something that will only embolden Russian dictator Vladimir Putin and other empire-minded autocrats.

• Climate. When oil executives complained about Biden's renewable energy and electric vehicle policies, Trump told the industry to raise $1 billion for his campaign, then vowed to reverse those Biden initiatives, according to the Washington Post. The overt suggestion of policy changes for the highest bidder is alarming, as is the lack of commitment to fighting climate change.

• Reproductive health care. Trump has taken credit for striking down abortion protections, saying in a 2023 speech that "I was able to kill Roe v. Wade." While he now appears to understand his party's vulnerability on this issue, he also chose a running mate in Vance who has supported a federal abortion ban and has opposed exceptions for rape and incest, though his views may have evolved. In contrast, Biden has wielded executive action to safeguard reproductive health care, including access to abortion medication, and his administration has defended women's right to this medical procedure during an emergency. Biden's successor must continue to make reproductive health care freedom a top priority.

• Protecting the Boundary Waters from mining. The Biden administration put in place a 20-year moratorium on risky copper mining near the BWCAW. Trump during his first administration installed industry lobbyists intent on allowing a Chilean mining conglomerate to open a mine in this sensitive watershed. The apparent pay-to-play offer for Big Oil also raises deep concerns about Trump kowtowing to the Chilean firm for the right sum.

Time may be short between now and Nov. 5, but there's still time for a healthy and informed campaign that focuses on these stark policy differences rather than age. Biden's selfless step has made that possible. His exit also stands in welcome contrast to Trump's graceless, selfish handling of his 2020 defeat. Biden deserves his nation's thanks for his time in White House and his decision to serve one term.