If either party can claim both the White House and Congress in next fall’s elections, there’s a huge prize for the taking: Unchecked power to reshape taxes for millions of Americans.

Much of the GOP’s sweeping Trump-era tax breaks are set to expire in 2025, which will almost certainly push Congress to act on their future. So the 2024 campaign will determine whether Republicans can keep the cuts, Democrats can rewrite them — or, if neither party gets a clean sweep, whether a split government prompts a massive fiscal collision.

The ability to mold the country’s tax structure may not ever become the primary focus of the presidential campaign or the battle for Congress. Yet both Democrats and Republicans are actively strategizing over how to handle the very real consequences of the tax cliff.

First, though, one party has to try to win it all.

“Anything at this point would be a wish list. Because it depends on what happens in 2024. It’s huge stakes,” said Sen. Rand Paul (R-Ky.). “You almost have to win all three branches: House, Senate and presidency.”

Both the House and Senate could remain closely divided in two years, but remaking tax policy can happen with simple majority votes thanks to congressional budget rules. That’s how a 50-50 Democratic Senate managed to impose a new corporate minimum tax last year, and how a 52-48 GOP Senate passed 2017’s massive tax law. It’s enough to raise the stakes of every single congressional campaign next year, because one or two House or Senate seats could make the difference between tax gridlock or one party rewriting the entire code.

Clear battle lines are already forming nearly two years in advance: Republican leaders say they would probably just try a straight extension of the expiring Trump tax cuts, particularly on income tax rates, though some have an appetite to expand or remodel them altogether. Democrats hate the cuts but are measured in how they talk about any repeal, aware that their rivals could easily attack such plans as a tax hike.

Democrats’ proposed tax increases on high earners stalled in the last Congress due to reluctance from Sen. Kyrsten Sinema (I-Ariz.) to touch income tax rates. She may not be alone in 2025 — Sen. Jon Tester (D-Mont.), who is defending his seat in a red state next year, said that when it comes to the tax cuts, “there’s probably some worth keeping.” President Joe Biden has vowed not to raise taxes on people making less than $400,000.

“We want the chance to do better” than the GOP on taxes, said Senate Finance Chair Ron Wyden (D-Ore.).

There’s early talk of a bipartisan tax deal before the election that would trade some corporate tax breaks for an expansion of the child tax credit, which is also on track to shrink further in 2025. The appeal of waiting may prove too great, however, since the trigger of expiring income tax rates creates more incentive for lawmakers to act.

Not to mention that the run-up to a presidential election year does not exactly create fertile ground for bipartisan agreement.

“It will be a campaign issue,” said Sen. Mike Crapo (R-Idaho), who would be in line to chair the Finance Committee if Republicans take back the Senate. “Democrats will claim that [Trump tax cuts] just help rich tax cheats. And the Republicans will say that bill gave us the strongest economy.”

It will be an intensely busy post-election year: The debt ceiling is also set to expire in 2025 (and can also be raised on a party-line basis), as are Obamacare subsidies that help keep some Americans’ health insurance rates lower. Rep. Brendan Boyle (D-Pa.), who’s in line to lead the House Budget Committee if Democrats can flip the chamber, drolly observed of the on-rush of 2025 policy cliffs: “Oh, you mean Armageddon?”

Sen. Mike Crapo (R-Idaho) would be in line to chair the Finance Committee if Republicans take back the Senate.