How money actually works in American elections

Abdul El-Sayed overcame a major financial disadvantage to win Michigan’s Senate Democratic primary. | Bill Pugliano/Getty Images The 2026 midterm cycle is projected to be the most expensive election cycle in US history, with candidates across the board raising money at a record pace.

And voters are taking notice: Big-donor groups tied to issues like Israel policy, AI, and crypto have become major flashpoints in primary races in both parties.

Campaign spending alone doesn’t determine elections.

The recent Democratic Senate primary in Michigan was the most expensive Democratic congressional primary in terms of outside spending — but ended with Abdul El-Sayed overcoming a major financial disadvantage to win the nomination.

In California, billionaire Tom Steyer spent over $200 million of his own money on his bid for governor , but lost.

But the ever-rising tide of cash helped fuel voter concerns about corruption and the campaign finance landscape is only getting more confusing: In June, the Supreme Court struck down limits on how much political parties can spend in coordination with their own candidates, further blurring the line between what candidates raise directly and what parties can spend on their behalf.

How can voters follow the money? How much difference does outside spending actually make in the outcomes of these races? And how much can candidates rely on grassroots donors to push back? Danielle M.

Thomsen , a professor of political science at the University of California Irvine and author of the 2025 book, The Money Signal: How Fundraising Matters in American Politics , has spent years studying these questions.

The conversation has been lightly edited and condensed for clarity.

Let’s start with a race like the recent Michigan Senate Democratic primary.

Abdul El-Sayed was massively outspent by outside interest groups like AIPAC and still won.

Does that change how you think about money’s role in politics, or is it generally consistent with what we know? The bulk of my research is looking at US House primaries, and I think you could probably draw similar conclusions for Senate primaries, except that in most cases, Senate primaries have way more information.

So in the case of Michigan, I think people knew largely what the choices were.

And after you get to that stage, largely through money and advertising and voter outreach, and campaigning, after that point, money might matter less because voters become more familiar with choices.