The newest Wall Street Journal/NBC News poll has some troubling news for Trump.

The poll released Friday found that of all the Republican presidential candidates, Trump has the least room to expand. He’s near his ceiling, and the race is just getting started.

Most candidates have a small segment of the population supporting them with plenty of room to grow, but because so many Americans say they could never vote for Trump, the business tycoon has a problem.

Trump’s volatile rhetoric and extreme positions on immigration have curried favor with much of the conservative base but have simultaneously alienated voters he’ll need to win a primary, and certainly a general election.

In June, two-thirds of Republicans said they couldn’t support Trump, though that number has dropped some. Now, 47 percent of Republican primary voters say they would be open to supporting Trump.

If Trump can’t even get half of Republicans to consider voting for him, he’s in for a tough battle.

Ben Carson, who is almost tied with Trump in the polls, has the most room to grow. Nearly 70 percent of Republicans say they would be open to supporting Carson.

The Wall Street Journal reports that based on this data, Trump “looks more like a middle-tier contender than the next Republican nominee.”