Trump's ultimate pitch: What he needs to do in next four days

RNC preps for Trump

CLEVELAND — Donald Trump has four days to accomplish two critical tasks in his extraordinary campaign for president.

The first is to strike themes capable of uniting his party and expanding its appeal. The second is convince Americans of his capacity to serve as commander-in-chief.

Both pose major challenges.

The bombastic billionaire trails Democrat Hillary Clinton by 46 percent to 41 percent in the new NBC News/Wall Street Journal poll. Among regions, he leads in the South but trails everywhere else. He leads among voters with only a high school education, but trails among those who attended college.

Donald Trump
John Sommers II | Reuters

He leads among whites, but not as much as Mitt Romney led President Barack Obama in his losing 2012 campaign. He trails among Hispanics by more than the 44 percentage points that Romney lost that fast-growing constituency by.

Trump took a first step toward unifying his party with his selection last week of Indiana Gov. Mike Pence as his running mate. Pence's experience in the House and the governorship, and his strong reputation among conservative Christians, reassured conventional Republicans.

The newly minted ticket has found its message in civil unrest at home and turbulence abroad, most recently in last week's attempted coup in Turkey. In an echo of past successful Republican campaigns, Trump calls himself "the law and order candidate." Driving home that message is expected to dominate the convention's first day Monday.

But Trump must also cross the threshold of acceptability as a potential president. A primary campaign driven by his reality-TV showmanship hasn't done that.

The good news for Trump is that political conventions, though drained of the suspense they held in an earlier era, remain huge communications opportunities. Some 30 million Americans saw Romney's 2012 nomination acceptance speech.

That was nearly one-fourth the number of people who voted in November. And record viewership of GOP primary debates suggests Trump will draw even more watchers this time.

Not until fall debates will Trump command an audience of that size at one time, with the chance at molding impressions of him. Using this moment well is critically important to his chances.