In the next few weeks there will be much interest in “bounces”—the jump in the polls that most presidential candidates enjoy after their party’s convention. Gallup has found that since 1964 Democrats have received an average 5.8% post-convention bounce and Republicans 4.9%. Actual performances vary from these averages. In 2012 President Obama jumped three points after his convention; Mitt Romney’s numbers remained virtually unchanged after his.
Donald Trump has been trending up in the polls this month, but to win he needs next week’s Cleveland convention to succeed. Doing that—leaving voters with the best impression of candidate, party and message—involves more going right than might be imagined.
First, Mr. Trump must unify the GOP. This means forgoing attacks on fellow Republicans, acting gracious toward party leaders who skipped the convention, and making the gathering about more than simply himself. He should emphasize the party’s values and the success of down-ballot candidates.
The presumptive nominee must avoid putting himself in situations like President Carter did in 1980, pathetically wandering the stage trying to get his primary challenger, Sen. Ted Kennedy, to raise arms together. By word, action and the convention’s programming, Mr. Trump must enthuse the Republicans watching on television who are lukewarm about his candidacy.
These tasks are critical for the candidate. To win in November, he must capture at least 90% of Republicans. The June 23 Washington Post/ABC poll had him carrying only 77% of Republicans. While Mr. Trump called the survey “very dishonest,” the June 28 Fox News poll found similar numbers, with Trump winning 74% of Republicans.
The two polls differed in how independents split. The Post/ABC poll had Mr. Trump winning them 45% to 43% while Fox put him up 39% to 31%.
Swing voters are the convention’s most important audience, especially those in battleground states. They typically pay less attention to politics, so impressions created in Cleveland will greatly affect their openness to vote Republican.
The convention must therefore present Mr. Trump in the best possible light—humanize him by dwelling on his background and family. But overdoing it risks the gathering coming off a personality cult.
Successful conventions also focus on critical issues and America’s future: Republicans must leave viewers with clarity about the GOP’s agenda. This requires far more than a good platform.
Everyone who appears on the stage—the candidate, keynote speaker, convention officials and others—should offer a forward-looking message about what a new Republican administration would do. This vision should be inclusive (we are all in this together) and appeal to the best instincts of ordinary Americans. Showcasing rising GOP leaders, especially young and diverse figures, can help.
It is critical that Mr. Trump’s message be one of constructive change: After a period of disunity and rancor, he should offer common purpose; after economic malaise, growth and prosperity; and after U.S. retreat and weakness, a return of American leadership and resolve abroad.
This will require message discipline in all his utterances, especially his acceptance speech. Over 30 million watched Mitt Romney’s in 2012, while more than 38 million tuned in to Mr. Obama’s.
The moment has an inherent tension. The hall is jammed with 20,000 screaming partisans, but Mr. Trump should resist the temptation to deliver his typical rally speech. His target audience isn’t those in the building but everyone watching on TV. Viewers at home don’t want to be whipped into a frenzy by whatever pops into Mr. Trump’s mind.
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