Who will break out? Who will break down?

Tribune News Service

CLEVELAND

Donald Trump needs to act presidential. Jeb Bush has to erase the notion that he’s just another Bush. And a host of Republicans have to make enough of a first impression on the American public that they can vault into the top tier of a crowded presidential field.

Ten Republicans will vie tonight from 9 to 11 in the first Republican presidential debate of the 2016 campaign. The other seven candidates can participate in a one-hour forum starting at 5 p.m.

The debate at Cleveland’s Quicken Loans Arena is likely to shake up and redefine the huge field, the biggest in modern times. Here’s what the contenders need to do to stay in, or reach, the front of the pack:

Tier One: The front-runners

DONALD TRUMP

Can he look and act presidential? He needs to show (a) he’s thought out some policy positions and (b) he has a commander in chief’s temperament. What’s his remedy for overhauling the nation’s health care system? Will there be some detail, or another burst of vivid sound bites?

JEB BUSH

Can he be pithy? And can he separate himself from his brother? The former governor of Florida tends to ramble and get too nuanced. Not a bad quality, but not a recipe for standing out in rapid-fire debates. He’s likely to get challenged on his support for a path to legal status for many undocumented immigrants and his support for Common Core standards.

SCOTT WALKER

Will he get beyond the talking points? The governor of Wisconsin wows Republicans when he boasts about how he took on unions in a budget fight. But it’s not all that it seems, and he’s likely to be confronted about shortfalls that required tough spending cuts. He usually answers with well-rehearsed talking points, but he must go further and impress viewers that he knows what he’s talking about.

MARCO RUBIO

Can he demonstrate gravitas and commitment? He has to defend his 2013 support for a comprehensive immigration overhaul that included a path to citizenship for undocumented immigrants, and then his move away from that approach. He wants to come across as a national security expert and needs to talk comfortably and authoritatively about terrorist threats.

Tier Two: So much potential TED CRUZ

Will he try to out-Trump Trump? Cruz can’t resist the quick hit, and it’s landed him in political jeopardy as Trump has won the outraged voters so far. The senator from Texas went for broke recently, calling the Senate Republican leader a liar. Will Cruz on Thursday separate himself further from the establishment?

RAND PAUL

What happened to him? He sank to eighth in the Fox News poll averages that determined debate status. The senator from Kentucky seems unable to get traction, even after this week’s leadership role in trying to divert federal funds from Planned Parenthood. TIER THREE: THE WILD CARDS

JOHN KASICH

Will conservatives accept him? He’ll be introducing himself to much of the public, and his regular-guy demeanor and ease discussing issues should help. But will the governor of Ohio appear presidential? And might he seem too centrist and accommodating to satisfy the conservative base?

MIKE HUCKABEE

Can he demonstrate mainstream appeal? He’s likely to keep pounding away with provocative statements, largely aimed at his Christian right constituency.

BEN CARSON

Is he too understated to make a splash? He’ll be steady, thoughtful, conservative, and maybe too calm and quiet to stand out.

The retired neurosurgeon has stayed away from the sort of incendiary comments that marked his early political efforts. But what does he know about how to fight terrorism or manage an economy?

CHRIS CHRISTIE

Can he calm down? His no-prisoners style is perfect for a debate. But the governor of New Jersey has to erase the impression that he’s too quick to anger when challenged. So far, he hasn’t demonstrated that ability.