Early voting begins today in Iowa. Though Trump has a healthy lead in the polls there, the state provides a key test for both Trump and Clinton.

For Trump, Iowa will be a proving ground of how well he can perform with the blue-collar voters that comprise the heart of his coalition. The state is both overwhelmingly white — 92 percent — and more poorly educated than the country is a whole: Just 26 percent of Iowans have college degrees compared with the national average of about 39 percent. So if Trump deliver in Iowa, it’s unlikely he’ll do so elsewhere.

That said, Barack Obama won Iowa twice — in fact, it was the only state in which he won working-class voters. This presidential election has been close in large part between Clinton, despite her vaunted campaign infrastructure, isn’t keeping the Obama coalition together. For her, a loss in Iowa would be a concrete indication of her political shortcomings, at least compared to those of the man she hopes to succeed.

My colleague Tim Alberta is on the ground in Iowa, so stay tuned for a report on early voting from him.