(Bloomberg) — Apple Inc (AAPL). has become a frequent target for attacks by President Donald Trump, a factor that has held the stock back as other big tech companies have rebounded over the past month.

The iPhone maker was the biggest company in the world at the start of May, but since then, it’s fallen to third, behind Microsoft Corp. and Nvidia Corp.

It underperformed again Wednesday, falling in a broadly negative session after OpenAI announced the acquisition of a startup co-founded by Apple veteran Jony Ive that is focused on artificial intelligence-fueled hardware. The prospect of shiny new alternatives to Apple’s devices added to concerns about the company’s struggle to compete in the AI arms race.

But a more unusual threat stems from Trump’s focus on the company over its global manufacturing process. Earlier this month, Trump said he “had a little problem with Tim Cook,” and said that he had asked Apple’s chief executive officer to stop building plants in India.

“It’s a red flag for me that Trump continues to single out Apple and seems to have something against them,” said Randy Hare, director of equity research at Huntington National Bank. “It doesn’t mean that Trump is going to do anything more, but you can’t predict what’s going to happen, and that makes me cautious.”

Shares fell 0.5% on Thursday, on track for their seventh straight negative session.

Political risk has been a driver of markets overall this year, as seen in Wednesday’s stock selloff over concerns about the ballooning deficit, an issue that prompted Moody’s to downgrade the US credit rating. Investors are also monitoring the latest developments regarding the Trump administration’s signature tax bill.

Apple’s fate has been more closely tied to the trade war and it has avoided the worst-case scenario that seemed plausible last month. While shares saw incredible tariff-related volatility and have recently been rangebound, the stock is still up 16% from the low it hit after the tariffs were first announced in early April.

Not long after, the Trump administration exempted key categories of electronics — including smartphones and computers — from its so-called reciprocal tariffs, and the US and China agreed to temporarily lower tariffs on each other’s products.

The CBOE Apple VIX, which tracks a market estimate of future volatility for the stock, has fallen sharply since hitting a five-year high a month ago.

Trump also praised Nvidia’s CEO for attending an investment forum in Saudi Arabia while noting that Cook didn’t.

“Trump pointing out that Cook isn’t at some summit makes the hair on the back of my neck stand up,” said Huntington National Bank’s Hare. “It doesn’t seem normal to me. Anyone who tells you they can quantify this risk is wrong.”