Beating Trump is a lot easier when he’s busy fighting fellow Republicans.

What’s going on?

Republicans have had a hard time uniting ever since the Tea Party insurgency swept into Congress in 2010. The only thing they could agree on was stopping Obama and the Democratic Party from accomplishing anything–a strategy on which they were at least partly successful.

But they’ve had problems working together for years. Under House Speaker John Boehner, it was impossible to get a budget passed with full GOP support. Some Democrats actually had to cross the aisle to keep the government funded. With Republicans now in control of both Congress and the Presidency, the situation has gotten even worse.

This right-wing fringe is most visibly represented in Congress by the House Freedom Caucus, led by Mark Meadows. Trump is upset that this group wouldn’t support the Republican effort to repeal and replace Obamacare, and how he’s steaming mad and out for revenge, going so far as to threaten to have Freedom Caucus members primaried out of their seats in 2018.

Why is it important?

This could be a huge deal for Democrats hoping to make inroads next year. Trump’s agenda can’t be defeated solely by focusing on 2020. It is necessary to try to take back Congress in 2018, too. All House seats and a third of all Senate seats will be up for re-election. Crucially, a lot of Democrats are up for re-election in the Senate, and it promises to be a tough fight. They are already looking ahead to that battle.

I’ll be honest: I’m not a big fan of Democrats, nor the Democratic Party as an organization. My views are further to the left and I have no love for the neoliberal consensus represented by the Obama/Clinton wing of the party. But Trump and the GOP are dramatically worse, and the damage they might inflict–indeed, are already inflicting–must be stopped.

How does Trump’s feud with the Freedom Caucus fit into this? It’s simple. If Republicans have to spend money fighting each other, it gives Democrats opportunities to take seats they otherwise may not have had a chance of winning. If Democrats can get behind candidates for any remotely competitive seat, and if Republicans can be encouraged to split their votes between Freedom Caucus extremists and non-ideological populists in the Trump mold, Democrats actually have a chance.

What can I do?

Find out what the Congressional races in your state and district look like for next year. Is there a Republican running unopposed? Do what you can to change that: support primary opponents, even vote in those elections next spring, if you can. It would be preferable for extremist GOP candidates to win those primaries if the seats are competitive, as an extreme candidate is more likely to lose against a reasonable candidate.

There will definitely be more to come on this topic. 2018 is a long way away, but it’s not that far off. We have to start thinking about it sooner rather than later. Trump definitely is.