With each party’s presidential nomination already secured by President Biden and former president Trump, today’s presidential primaries in Arizona, Florida, Illinois, Kansas and Ohio might not be getting their typical level of election season attention or voter turnout. But, the handful of down-ballot races now in the limelight are an important reminder of the highly consequential congressional races set to take place alongside the race for the White House this November.

As it stands, Democrats have a one-seat majority in the Senate. This November election, every House seat and 34 Senate seats will be up for election; and of those 34 Senate seats, 23 are currently held by Democrats and 11 are held by Republicans. That means, to maintain their majority in the Senate, Democrats cannot afford to lose more seats than they gain.

This won’t be easy. Senator Joe Manchin’s West Virginia seat is primed for a Republican pickup and at least three other seats are considered a toss-up. One of those is in Ohio, where today’s primary determined the Republican (Trump-endorsed Bernie Moreno) who will take on Democratic Senator Sherrod Brown and possibly lead Republicans to a Senate majority from 2025.

Legislative stagnation in Congress over the last two years – difficulty passing bills that impact AUKUS, the US debt ceiling, and aid for Ukraine and Gaza – demonstrates that the composition of Congress can be just as consequential for US foreign policy as the personality of the president. While the nominees for both major parties are decided, the implications of the 2024 US election are far from sure.