Republican candidates for the U.S. Senate in New Hampshire, Pennsylvania, North Carolina and a few other key states are struggling under the weight of Donald Trump’s candidacy. But there seems to be at least one exception: Republican Sen. Rob Portman of Ohio.

Polling released in the past few days — including a Monmouth University survey of Ohio released on Monday — confirms that Portman is not being swamped by the anti-GOP sentiment Trump is stirring up. The Monmouth poll found Trump down by 4 percentage points and Portman ahead by 8.

The new Monmouth survey is in line with the polling averages: Portman holds a clear advantage over Democrat Ted Strickland, leading in all four polls taken since both conventions ended. And in that time, Portman has expanded his lead while Trump’s position has deteriorated. Trump trails Hillary Clinton by 4 points in Ohio, according to our polls-only model, while he trailed Clinton by about 1 point just before the GOP convention started. But Portman leads Strickland by a little over 7 points, on average, in post-convention polls. In the month before the conventions, Portman led Strickland by an average of just 1 point.

How is Portman resisting Trump’s downward pull? Here are three factors that may be helping him separate himself from the presidential nominee in the eyes of Ohio voters:

Of course, it’s still August. Portman’s position could worsen if Trump’s numbers stay where they are. Or Portman could run into his own issues.

The bigger question is whether other Republicans can copy from the Portman playbook. I’d bet against it: Portman is a unique personality in a uniquely anti-Trump state with an unusual fundraising advantage. Still, Portman’s ability to keep Trump at a distance should give Republicans some hope in their quest to hold the Senate majority. Although Democrats have leads in enough races to take control of the chamber, their leads are small enough in enough states that it’s far from a sure thing — if more GOP Senate candidates can copy Portman, it could help the party keep the Senate.