Republicans in Congress will lose power at the start of January, and they won’t get it back soon.

But they still have eight weeks until then.

They’ll need to get to work.

There’s a long history of achievement in lame-duck sessions with the outgoing Congress.

More than a dozen Supreme Court justices have been confirmed in a lame-duck session, including legends such as Chief Justice John Marshall and Justice Oliver Wendell Holmes, and the Thirteenth Amendment banning slavery was passed by a lame-duck Congress.

Sometimes, Congress has done big things even after a major election loss swept one party out of power.

But major obstacles lie ahead.

The Senate filibuster means that Democrats can stop almost any legislation except for tax, budget and debt-ceiling bills that use the budget reconciliation process.

Even for bills that have bipartisan support, Democrats may prefer to wait until they can negotiate a better deal with their big new majorities.

That could be the fate of farm bills and the bipartisan Protect College Sports Act, which already passed the Senate and regulates things like the rights of athletes to cash in on their name and likeness.

The reconciliation process is cumbersome.

The easiest thing is to confirm judges, which requires only a majority in the Senate — but that faces its own obstacles: Keeping the Republican Senate caucus together won’t be easy.

Because he won a special election to fill JD Vance’s old seat, Sherrod Brown will be sworn in immediately, dropping the GOP Senate majority to 52.

Mitch McConnell is still in poor health; Tommy Tuberville and Marsha Blackburn will be busy in Alabama and Tennessee, where they were just elected governor.

Some departing incumbents, such as John Cornyn and Thom Tillis, are still bitter at President Donald Trump, while swing-state Republicans such as Wisconsin’s Ron Johnson, Pennsylvania’s Dave McCormack and North Carolina’s Ted Budd will be nervously looking at their next election.

Lisa Murkowski of Alaska is never a reliable vote.

On the House side, Speaker Mike Johnson has little leverage with his four-seat majority, and his own issues with members such as new Florida governor Byron Donalds, who are focused on their next job.

With Democrats in no mood to allow any more new judges, Republicans should get a move on.

But there are no unfilled vacancies on the federal appeals courts, and Trump has sent the Senate nominees for only 11 of the 28 open district judgeships.

With time short, few federal judges and likely no Supreme Court justices would be willing to resign now, knowing their spots might go unfilled for two years if the Senate runs out of time.

A government shutdown looms in December if nothing gets passed — and again, Democrats will have no incentive to play ball.

Republicans also want to raise the debt ceiling, a move entirely aimed at reducing Democratic leverage, and add more defense spending.

The defense budget should be a priority, but some gun-shy Republicans may balk at funding to extend operations in Iran when many in the party are blaming that war for their wipeout.

There’s also not that much point trying to pass measures that Democrats will be able to easily repeal, or pushing new voting rules or other laws that will trip up a reconciliation bill because they’re not authorized by the parliamentary rules.

It’s worth holding members’ feet to the fire and giving them the minimum time off for holidays when this is the last chance for some time to pass a reconciliation bill. Sen. Bernie Moreno has called for a “Last Supper.”

But Republicans should focus on delivering things that matter to their constituents — not funding Trump’s ballroom and other construction jobs.

Triumphal arches are for winners.

Dan McLaughlin is a senior writer at National Review. X: @BaseballCrank