Has Trump hit his ceiling?

In poll after poll, Trump isn’t even close to winning a majority of the vote. While he’s narrowed the gap between his campaign and Hillary Clinton in recent weeks, in the past 21 national polls conducted using conventional phone or internet methodologies over the last five weeks, Trump’s high-water mark in a head-to-head matchup with Clinton is 44 percent.

And when third-party candidates — Libertarian Gary Johnson and Green Party nominee Jill Stein — are included, Trump’s highest poll score is only 40 percent, well below Clinton’s high of 50 percent.

The GOP presidential nominee’s limited support isn’t necessarily prohibitive for his chances — especially if Johnson and Stein continue to draw, combined, more than 10 percent of the vote. He only trails Clinton by 4 percentage points in the RealClearPolitics average and by 5 points in the HuffPost Pollster model. But if support for the third-party candidates dwindles closer to Election Day, Trump’s inability to expand his base could tilt the race further toward Clinton or require him to find a way to win with only a plurality of the vote, rather than a majority.