Election 2026: Republicans' most vulnerable congressional races

Judging by the latest polls, Republicans are clearly feeling the heat with election day due tomorrow. Earlier today, the stakes for US President Trump and the financial markets were already examined. The focus now turns to where exactly Republican control of Congress could come under threat in the midterms.

Put simply, these are the contests worth watching tomorrow.

Start with the Senate. Democrats need a net four seats to take control away from Republicans there. Recent polling points to several Republican-held seats being in competitive races.

The other side of that equation matters just as much. Democrats also have seats they must defend, above all the open race in Michigan. Without holding those, any Republican losses elsewhere could be made up.

The House follows, and its landscape is even more tangled.

Cook Political Report's ratings from last week put 14 of the 18 House seats listed as toss-ups in Republican hands, and a further 13 Republican-held seats are classed as leaning Democratic. That is a hefty number. With so many districts to track, anyone following just a few would need to choose carefully.

It is worth remembering that these figures are only snapshots of the electoral landscape. A polling lead is not a guarantee, and the way votes translate into seats can still throw up a surprise or two.

In any case, the main thing I would watch is whether Republicans are losing competitive House districts faster than expected and whether Democrats are gaining ground in several Senate battlegrounds at the same time.

That is what markets must factor in, as an unexpected outcome or a sharp shift away from forecasts could trigger repricing in Treasury yields and the dollar.

All the same, tomorrow is about more than who wins and who loses. Ultimately, it is a major test of how much room to manoeuvre Trump will have left for the rest of his presidency.