The ten Republican candidates who made Fox News’ cut-off for Thursday's first primetime presidential debate (sorry, Rick Perry) agree on policy more than they differ. Still, each has at least one position that sets him apart from the rest of the field—and from mainstream Republican thought. It makes the debate worth watching, not just for Donald Trump's bombast, or to see who gets in the best zinger. There are serious issues at stake in the election, and this debate is an opportunity for the candidates to separate themselves from the rest of the pack. One false move, though, and these issues could haunt them on the campaign trail. 

Here are some things to watch for on Thursday night:

Donald Trump

Even though the Supreme Court has upheld the Affordable Care Act—twice—you’re still likely to hear candidates promise to “repeal and replace” the law. While the frontrunner hasn’t divulged much about his own policy agenda (his foreign policy, for instance, includes offending an entire country and promising a “foolproof” plan to defeat ISIS), he does endorse a version of comprehensive health reform with a single-payer system for the poor. In 1999, Trump considered running for president on the Reform Party ticket, and said at the time that he supported a “comprehensive health care program" and would fund it through increased corporate taxes. Though Trump's changed his mind at times since then, in late July he defended his early stance. “We have to take care of people that are poor,” he told a conservative radio host.

Jeb Bush

Bush has flirted with a more moderate environmental platform, and conservative green donors hold out hope that he has more to offer on climate change than any other GOP candidate with a realistic shot at the White House. After all, Bush has come the closest of any of the top 10 to admit that climate change is a man-made problem, and he sponsored conservation efforts as Florida’s former governor. The only problem: He still thinks market disruption from the gas boom is enough to fix the climate, without any federal regulations.

Scott Walker

On immigration, Walker hints that he will run to the right of the entire field, by endorsing the idea of reducing legal immigration. On Thursday, candidates will likely discuss the need for tackling undocumented immigration, but Walker has actually embraced the nativist approach. "The next president and the next Congress need to make decisions about a legal immigration system that’s based, first and foremost, on protecting American workers and American wages,” Walker said in an April interview. And he’s aligned himself with a far-right senator, Jeff Sessions, who has been a fierce critic of President Barack Obama's immigration policies.

Mike Huckabee

Party consensus deems entitlement reform necessary to ensure the country's fiscal health, Huckabee has made a calculated bet to defend these programs. "There are some who propose that to save the safety nets like Medicare and Social Security, we ought to chop off the payments for the people who have faithfully had their paychecks and pockets picked by the politician, promising them that their money would be waiting for them when they were old and sick," Huckabee said in his May campaign announcement. "If Congress wants to take away someone's retirement, let them end their own congressional pensions, not your Social Security."

Ben Carson

In May, Carson backed raising the federal minimum wage from its current rate of $7.25 an hour—an unusual position for a party that normally reverts to the line that it’s an issue best left to states to decide. "I think probably it should be higher than it is," he told CNBC’s John Harwood. Carson also doesn’t think the government should cut welfare benefits until it cuts taxes.

Ted Cruz

Cruz is the GOP’s base incarnate, or at least he says he is. At his campaign launch in March, he described his candidacy as a “grassroots guerrilla campaign.” Republican elites don’t like his tactics, which include a habit of holding the debt ceiling hostage. And he doesn’t offer many specifics on policy. Of what he has done in the Senate, pundits think he’s too conservative on federal spending, same-sex marriage, immigration, and more to gain much traction as a presidential candidate. 

Marco Rubio

Rubio still supports a pathway to citizenship for undocumented immigrants, after focusing on border security. “Once you have permanent residency, which is a green card, existing law allows you to apply for citizenship,” he told the New York Times in January. Also, he’s proposed an anti-poverty platform that expands the Earned Income Tax Credit (EITC) to include childless working adults, as a lift to the working poor. Republicans are more likely to criticize the tax credit than to expand it (the EITC was the inspiration for Mitt Romney’s “47 percent” speech about half of America not paying income taxes). And Rubio’s plan has similarities to Obama’s proposal for reform. However, to keep it deficit-neutral, Rubio’s tweak would likely come at the expense of low-income adults with children.

Rand Paul

Paul has made some overtures to African-American voters during primary season—supporting decriminalizing marijuana and reducing mandatory sentencing—while most of his party has leaned on dog-whistle politics. Sometimes, Paul's insensitive rhetoric and controversial history on the Civil Rights Act have backfired. But Paul is also rare among Republicans in condemning civil asset forfeitures and sealing the records of nonviolent juvenile offenders. "If you smoked some pot or grew marijuana plants in college, I think you ought to get a second chance," he said in a March speech at a historically black college.

Chris Christie

The New Jersey governor wants to raise the retirement age and cut other entitlement spending but broke from the party line to expand Medicaid under Obamacare, a move that has helped more than 400,000 residents. Christie’s history on gun control also bothers conservatives. Although he vetoed more recent gun control bills, including one that reduced the size of ammunition magazines, in the past he’s called for striking the “right balance” between public safety and the Second Amendment. The National Rifle Association has taken note: Christie wasn’t invited to their annual conference this summer and earned a “C” grade from the group.

John Kasich

The Ohio governor chose to expand Medicaid in his state under the Affordable Care Act, one of only ten GOP governors to do so. In an interview with CNBC in July, Kasich defended accepting federal dollars, saying “It’s money we sent from our state of Ohio to Washington that I was able to bring back to help the mentally ill get on their feet.” He added that other Republican governors have followed suit. “So I was just an early mover, but the fact is, overall, we have a healthier society.”

Some of these issues have already proven problematic for the candidates. While Trump has surged, Bush has been slipping with the conservative voting block—from 70 to 55 percent in a month according to a Wall Street Journal/NBC poll published this week. Making it to the primetime debate means the bevy of candidates will now face more scrutiny for their positions.