To the Editor:Dear Joe (may I call you Joe?):Do the possible.There is a mess of massive proportions to clean up. Some problems can be fixed quickly, like Deferred Action for Childhood Arrivals. Some can be fixed over time, like our declining status in the world. And some can never be fixed, try as you might.If you believe you can “bring us together,” and bridge the cataclysmic divide we face, you are a bigger dreamer than the DACA children. Do the possible. Clean up and depoliticize the Justice Department, and keep your finger off the scale. Get us on the right side of the climate change fight. Reintroduce us to our allies. Get some infrastructure upgrades started; even some Republicans will agree with that.Make your government look and speak like America. Insist on accountability, even for the rich and powerful. You can do all of this and much more. And whatever else you do, don’t forget who elected you.Don’t expect much help from the Hill. Congress is badly broken, probably for the foreseeable future. Use what you have in the presidential toolbox. Do the possible.Richard WilsonOrlando, Fla.To the Editor:The biggest challenge facing Joe Biden’s presidency is Mitch McConnell. Use every ounce of charm and political skill you’ve got in you, Joe. If we can get Mr. McConnell to get behind creating millions of new jobs and reviving the economy by rebuilding our infrastructure, developing renewable energy and bringing manufacturing back to our soil, voters from both sides of this divided country are going to benefit.It’s the only way to start bringing the two sides together. Turn Mitch McConnell into part of the solution, Joe.Judith CressyNew YorkTo the Editor:The greatest challenge facing President Biden will be the simple fact of governing. That is because his opposition — the Trump Republican Party — will do everything in its still formidable power to undermine him. At every turn. Through means legal and otherwise. The members of that opposition have long since given up any claim to governing in the public interest; it is their own interest, and only that interest, that motivates them.Unfortunately, Mr. Biden will attempt to govern the way he’s operated throughout his political life, that is, by constantly “reaching across the aisle” in an appeal to reason and unity. But the Republican Party, even before President Trump took ownership, is not open to such appeals, as was evident every time President Barack Obama reached across the aisle, only to find that he extended his hand into a nest of vipers.One should not try to make nice. I pray that Mr. Biden and Kamala Harris will acknowledge their opposition for what it has become, not what they think it should be.Nathan WeberNew YorkTo the Editor:The biggest challenge President Biden will face is the ability to focus on the real problems at hand. Covid-19 is raging, our economy is sputtering, many families are on the brink of destitution, to mention a few of the challenges. And complicating these daunting challenges are the calls for accountability for the crimes President Trump has allegedly committed.We can spend the next four years trying to prosecute Mr. Trump. It might be successful and satisfying — but at what price? If we do, surely he will continue to be in the spotlight, and the source of disinformation.My humble alternative: Come Jan. 20, forget Mr. Trump, take him out of the spotlight, and let the New York prosecutors feast on him! Let’s rally behind President Biden’s calls for a bold rational response to Covid, a climate-based investment in our economy and relief for those in need. And let’s (re)create a Democratic Party that pays attention not only to the coastal folks (like me), but also to our brethren in the industrial belt and farms of America.Lastly, President Biden should propose key government reforms — presidential accountability, criminal liability, access to tax returns — that would ensure we never have another Trump.Mark ZillHighlands, N.J.To the Editor:President-elect Joe Biden: Do not issue a blanket pardon to President Trump. He would only use it as “proof” to his followers that he has done nothing wrong and that any claims of wrongdoing were all a charade.Mr. Trump has worked to divide our country and to use his office to promote his own interests. He has immeasurably weakened our country and our standing in the world. He has shown utter contempt for the institutions of our government, for our democracy and for the very lives of our people.Our justice system is strong. Our society is strong. As a society, we need to face the damage that Mr. Trump has done to our nation, his alleged violations of federal tax laws and his self-dealing. Only after that would it be conscionable to consider any form of clemency or pardon.The failure to hold Mr. Trump accountable would demonstrate the United States’ weakness as a nation of laws.James JonesManasquan, N.J.To the Editor:Climate, climate, climate, it’s the climate, stupid.There are many challenges facing Joe Biden’s presidency — Covid, a struggling economy, systemic racism, income inequality, police reform, immigration reform, infrastructure, just to name a few.None of these come close to the challenge of climate change, either in scope or long-term ramifications. I believe that most Americans don’t think it is a hoax and agree it needs addressing, but moneyed interests and the tribal condition of our politics make it much harder to do so.Joe Biden and his team understand the problem and have a good plan to begin to address it. My advice to him would be to keep the focus on this issue as a top priority and to remember that a green economy is good business. For the most part, I support the Green New Deal, as well as the Blue New Deal for our oceans, which doesn’t get much attention. I believe there are plenty of pieces of both deals that a Biden administration can pursue, without getting mired in the pitfalls of partisan politics.Thomas HoopesIpswich, Mass.To the Editor:While curbing polarization and a pandemic are undoubtedly the most pressing issues facing the president-elect, I suspect that the greatest challenges of Joe Biden’s tenure in office will be abroad.The chaos of domestic politics in the last four years has distracted the American public from a worsening international landscape. In the Middle East, Mr. Biden will face an aggrieved Iran; in Asia, a beleaguered Hong Kong; in Africa, a brewing Ethiopian civil war. President Trump may have bombed ISIS to smithereens, but he worsened U.S. relations with key allies while building bridges with autocrats.Members of Mr. Biden’s State Department have their work cut out for them, from rebuilding the World Trade Organization to restraining the excesses of regimes like Recep Tayyip Erdogan’s in Turkey, which have been given free rein under the Trump administration.My advice to Mr. Biden is to repair American foreign policy, while avoiding the moral compromises of the Obama administration, such as the shameful drone program and the failure to end the extrajudicial imprisonment at Guantánamo Bay.Ravi SimonFramingham, Mass.To the Editor:My advice for President-elect Joe Biden on avoiding pitfalls: Please, please don’t tweet. And require your staff not to.Stephen di GirolamoAlexandria, Va. More