(AP Photo/Carolyn Kaster)

A new Gallup poll finds that a bare majority of Americans say the GOP convention made them less likely to vote for Donald Trump, the first time Gallup has ever found this in three decades of post-convention polling:

By 45% to 41%, Americans say they are more rather than less likely to vote for Hillary Clinton based on what they saw or read about the Democratic convention. In contrast, many more Americans said they were less likely (51%) rather than more likely (36%) to vote for Donald Trump as a result of what they saw or read about the Republican convention.

Gallup has asked this question about Democratic and Republican national conventions since 1984, with the exceptions of the 1984 and 1992 Republican conventions. The 2016 Republican convention is the first after which a greater percentage of Americans have said they are “less likely” rather than “more likely” to vote for the party’s presidential nominee.

I’ve obtained a demographic breakdown of these responses from Gallup senior editor Jeffrey Jones, and the numbers suggest that Trump’s convention might have pumped up his base, but it didn’t do a great deal to broaden his appeal.

Trump’s convention made white men and blue collar whites more likely to vote for Trump:

— 52 percent of white men say the convention made them more likely to vote for Trump, while 33 percent say it made them less likely to do so.

— 52 percent of whites who didn’t graduate from college say the convention made them more likely to vote for Trump, while 36 percent say it made them less likely to do so.

But Trump’s convention made white women, college educated whites, independents, and young voters less likely to vote for Trump:

— 41 percent of white women say the convention made them more likely to vote for Trump, while 48 percent say it made them less likely to do so.

— 36 percent of college educated whites say the convention made them more likely to vote for Trump, while 48 percent say it made them less likely to do so.

— 28 percent of independents say the convention made them more likely to vote for Trump, while 54 percent say it made them less likely to do so.

— 23 percent of voters aged 18-29 say the convention made them more likely to vote for Trump, while 61 percent say it made them less likely to do so.

Trump needs to expand his appeal among white women and college educated whites in order to win the White House, because he probably can’t win by driving up huge turnout and margins among white men and blue collar whites alone. But as Gallup senior editor Jones told me today, Trump’s convention appears to have done little to win over some of the groups he needs to improve among in order to accomplish that goal.

“He did appeal to some proportion of white women and white college graduates, but he certainly turned off more than he appealed to,” Jones said. “At the end of the day, he was worse off than where he started.”

This dovetails with what many have suggested about Trump’s candidacy — and Trumpism writ large — specifically, that it is driving a cultural gulf between non-college and college educated whites. The convention featured a good deal of choreographed anger at Hillary Clinton — the chants of “lock her up,” the parade of denunciations of her handling of Benghazi — as well as a vivid portrait of an America that is facing dire threats from skyrocketing crime, hordes of invading illegal immigrants and terrorist-refugees, sinister elites who have enriched themselves at the expense of the American worker, and so forth. Some polls have shown that blue collar whites agreed with Trump’s depiction of the country, while college educated whites did not.

After the GOP convention, Democratic strategists told Ron Brownstein that they saw an opening to highlight Trump’s disqualifying temperament and his rejection of diversifying America, with the goal of “maximizing their margins and turnout” among the voter groups “at the core of their modern coalition,” which include Millennials and secular college educated whites, especially women. As Brownstein noted, Trumpism is forcing an acceleration in the “class inversion of American politics,” in which Trump is performing very well among blue collar whites but is on track to becoming the first GOP nominee to lose among college educated whites in half a century.

Indeed, the Democratic convention also appeared designed to accelerate this class inversion. It was heavily focused on reaching out to college educated whites and suburban white women, through drawing a sharp contrast between the Democratic Party’s increasing embrace of culturally and demographically evolving America, and Trumpism’s reactionary hostility towards it.

To be sure, there’s no telling what the lasting impact of the conventions will be. Trump did receive a bounce from his, though it appears to be modest. And it’s still too early to say what sort of bounce Clinton will receive, though the early polling suggests it will be larger than Trump’s. We don’t know how long any of this will last in any case. But if conventions are designed in part to broaden the appeal of a nominee and his party, Trump’s convention appears to have fallen short of that goal.

Of course, it’s perfectly plausible that Trump thinks he can win mainly by riding a wave of angry white men and blue collar whites into the White House, and geared his convention towards that one overriding goal. If so, it may have been a smashing success.