Republicans are bracing for an ugly November. The GOP House majority looks lost, and Democrats are increasingly confident of capturing the Senate. Divided government lies ahead, along with obstruction and investigations. "I'm going to be impeached," President Trump told South Carolina voters in August. "They're going to impeach me. They have no idea why."
Impeachment may be the least of Mr. Trump's worries. After all, he's been through it twice. What he hasn't experienced is full Democratic control of Congress. It would make all his problems worse.
The president might believe he would be able to dismiss a Speaker Hakeem Jeffries as a nuisance, as he did Speaker Nancy Pelosi in his first term. He won't have that luxury if Chuck Schumer is also Senate majority leader. A Democratic Senate would be impossible to ignore.
Nor would the pain end for Republicans when Mr. Trump leaves office. Senate elections have a long tail. Six-year Senate terms are spread across presidential administrations, giving senators many chances to serve in the majority, influence policy and cast defining votes.
The senators who win this year won't be up for re-election until 2032, the end of the next presidential term. They will become the base of support for, or a bulwark against, the legislation and appointments of Mr. Trump's successor. Some may try to become that successor.
This has happened before. Democrats netted six seats in 2006 and gained Senate control. Sherrod Brown, Bob Casey Jr., Claire McCaskill, Jon Tester, Jim Webb and Sheldon Whitehouse opposed George W. Bush during his last years in office, for sure. But their true impact wasn't felt until 2009, when they voted for President Obama's stimulus bill and ObamaCare.
Conversely, Republicans gained nine seats and a Senate majority in 2014. The class of '14 included conservative stars Ben Sasse, Tom Cotton and Joni Ernst, who helped sustain Majority Leader Mitch McConnell's 2016 hold on Merrick Garland's nomination to replace Justice Antonin Scalia. And when Donald Trump became president, they all voted for Mr. Trump's Supreme Court nominees and the Tax Cuts and Jobs Act.
Even small gains in the Senate can have major consequences. Democrats won two Senate seats in 2018 (while losing four), yet Kyrsten Sinema and Jacky Rosen went on to vote for President Biden's spending deluge. Democrats won both Georgia Senate seats amid the 2020 election debacle -- aiding Mr. Biden and providing a presidential springboard for Jon Ossoff.
Though Republicans lost a Senate seat in 2022, one GOP senator elected that year found himself as Mr. Trump's vice president in 2025, casting the tie-breaking vote for the One Big Beautiful Bill Act. Americans who cast votes this year in protest might wind up launching the career of the Democrats' JD Vance. Also recall 2004, when an open Senate seat in Illinois served as the launch vehicle for Mr. Obama.
Here's what a Democratic Senate might do: Not only would Democrats stop Mr. Trump's legislative agenda. They would amplify the progressive tax, spending and regulatory bills that come from a Democratic House. President Trump's veto pen would be busy.
At the same time, Senate Democrats would block presidential appointments. The Supreme Court wouldn't be exempt. Democrats have been thirsting for revenge since Sen. McConnell blocked Mr. Garland's nomination. Winning the Senate in November would give them that chance in the event of a vacancy.
Thwarting Mr. Trump would be only the start. Democrats in Congress will use policy and messaging to soften the ground for the 2028 presidential campaign. And if a Democrat wins in 2028, he could, like every first-term president since Bill Clinton, take office with a unified government. Then the conservative nightmare begins.
By 2029, potential Democratic members of the class of 2026 -- Roy Cooper, Mr. Brown, Mary Peltola, Josh Turek, Abdul El-Sayed and company -- would all be ensconced in the Dirksen, Russell and Hart office buildings. They'd be eager to cast votes for the next Sonia Sotomayor or Ketanji Brown Jackson. They'd be champing at the bit to end the legislative filibuster.
That would open the door for bills to override state-based election laws, including voter ID, to impose term limits on or add seats to the Supreme Court, and grant statehood to the District of Columbia and Puerto Rico. Senators elected under the banner of "affordability" would be positioned to raise taxes, limit oil and gas production, expand government and muck with health insurance -- a lefty free-for-all.
A Senate election has lasting consequences. That is even more reason for Republicans to make a priority of spending in races that could tip the balance of power. Mr. Trump may agree with Democrats that the election is about him, but it is also about setting the stage for what comes after him. Mr. Trump might not be on the ballot this year. The future of American politics certainly is.
Mr. Continetti is a columnist for WSJ Opinion's Free Expression.
(END)