America’s gross national debt topped $35 trillion for the first time on Monday, a reminder of the nation’s grim fiscal predicament as legislative fights over taxes and spending initiatives loom in Washington. The Treasury Department noted the milestone in its daily report detailing the nation’s balance sheet. The red ink is mounting in the United States more quickly than many economists had predicted as the costs of federal programs enacted in recent years have exceeded initial projections. The leading presidential candidates, Vice President Kamala Harris and former President Donald J. Trump, have said little about the nation’s deficits on the campaign trail, suggesting that the economic problem will only worsen in the coming years. Deep differences between Republicans and Democrats on policy priorities and resistance within both parties to enacting cuts to the biggest drivers of the national debt — Social Security and Medicare — have made it difficult to reduce America’s borrowing.