What happens when a politician breaks a major campaign promise? The intuitive answer is that voters punish them. But recent scientific research suggests the political consequences are considerably more nuanced.
That question is particularly relevant for Donald Trump and Republicans heading into the 2026 midterm elections.
In his first midterm election in 2018, Donald Trump campaigned aggressively for Republican candidates across the country. The result was that Republicans lost 42 House seats and control of the House of Representatives. And that was without unpopular tariffs and an even more unpopular war on Iran.
Trump ran for president presenting himself as an opponent of prolonged foreign wars. Whatever one thinks of the decision to go to war with Iran, the political tension between that positioning and the current conflict is difficult to miss.
On paper, that looks like a textbook broken campaign pledge. But does breaking a promise actually cost a politician votes?
A recent study published in The Harvard Journal of Press/Politics, provides an intriguing answer. Based on four experiments involving more than 7,000 participants in the United States and Israel, the researchers found that the political consequences of broken promises depend heavily on context.
Prior opinions and partisanship matter.
If voters have little prior knowledge of a politician, breaking a promise can significantly damage both their evaluation of the politician on the specific issue and their overall opinion of that politician. But the picture changes when voters already know the political figure and have established attitudes toward them.
When voters are asked about a politician that they have a favorable opinion about, they start to rationalize or even apologize for a broken campaign promise. I have actually observed that behavior myself unfolding in focus groups I have conducted for clients.
Or, a broken campaign pledge may impact how voters view the politician on that specific issue, but it may not necessarily lower their overall approval of the politician in question.
For sure, the war with Iran is unlikely to be politically helpful to Trump or Republican candidates. But the negative impact might not be as big and as automatic as some Democrats assume.
After all, Trump is one of the most familiar and polarizing political figures in America. Most voters already have strongly established opinions about him. As a result, the key for Democrats will be whether they can tie the war on Iran to what voters care most about, which is inflation.
Broken campaign promises matter, but they do not operate in a political vacuum.