Staff prepare for the second official Republican primary debate at the Ronald Reagan Presidential Library in Simi Valley, Calif. on Wednesday. (REUTERS/Lucy Nicholson)

The 11 Republican candidates participating in Wednesday night's prime-time primary debate on CNN agree with each other on most issues. Viewers will get a good overall view of where the Republican Party stands going into next year's presidential campaign.

The candidates think that government can be made more efficient, and they oppose what they see as federal interference in private life. In particular, they don't think that the government should act to prevent climate change, either because they don't think it's real or because they don't think it should be a priority.

On points where some Republicans have disagreed in the past, consensus has emerged. While some -- including Jeb Bush, the former governor of Florida, and Carly Fiorina, the former head of Hewlett-Packard -- have argued for legal status for undocumented immigrants, all now agree that the border must be secured first.

The field is now in agreement on foreign policy, too. For some time, observers thought that Sen. Rand Paul (Ky.) might have offered an alternative to the party's hawkish tone, but he, too, has recently taken a harder line on American negotiations with Iran.

On several important questions, though, there are real differences of opinion. And since the first Republican debate on Fox News last month, the candidates have said more about their positions, providing new material for the debate's moderators (CNN's Jake Tapper and Orange County, Calif. radio host Hugh Hewitt).

Below are three hot topics that could make things interesting Wednesday night.

Abortion

Most of the Republican candidates are staunchly opposed to legal abortion. Sen. Marco Rubio (Fla.) and Mike Huckabee, the former governor of Arkansas, suggested that the Constitution protects unborn children during the last debate. Wisconsin Gov. Scott Walker reiterated his position that abortion should be illegal without exceptions for cases in which giving birth would put the mother's life in danger.

Donald Trump, the frontrunner in the polls, also favors a ban on abortion. It is a new position for him, and there is some ambiguity about whether he supports exceptions for women early in their pregnancies. Ben Carson, the runner-up, describes himself as pro-life and is opposed to abortion personally, but he thinks that individual women should make their own decisions.

"You cannot legislate morality," a spokesman for Carson told Politico, declining to name any additional legal restrictions on abortion that the candidate supported.

Abortion was a major theme in last month's debate, but it is not a simple issue. The candidates still have plenty to discuss with regard to whether abortion should be banned and, if so, which exceptions should be allowed.

Entitlements

Social Security and Medicare have always presented a political challenge for Republicans. Conservative politicians whose goal is to reduce the size of government would like to address the fiscal shortfalls in these programs over the long term by reducing benefits, not raising taxes. Yet the elderly are an important Republican constituency and also generally skeptical of reforms that would reduce benefits.

Bush, Carson and New Jersey Gov. Chris Christie have proposed some combination of raising the retirement age and limiting benefits for wealthier Americans -- while stressing that their proposals wouldn't affect current retirees. Trump and Huckabee, by contrast, oppose reductions in benefits.

Carly Fiorina has taken yet another approach to the perilous politics of Social Security. She declined to answer a question about entitlements from CNBC's John Harwood in an interview published Wednesday, saying she would not discuss the issue until after the election.

"I am not prepared to go to the American people and talk to them about how we're going to reform Social Security and Medicare until I can demonstrate to them that the government can execute with excellence," she said.

Perhaps Tapper or Hewitt will ask her that question again Wednesday night.

Taxation

There is a wide range of views among the Republican candidates on tax policy. Huckabee, Paul and Carson have proposed versions of a flat tax, which would substantially reduce taxes for the wealthiest Americans. Huckabee would levy the tax on consumption rather than income, and Carson would not exempt the poor from the tax.

[Read more: The new Republican tax plan is just the Bush tax cuts on steroids]

Supporters of a flat tax believe that taxing the rich at higher rates penalizes them for success and discourages people from making contributions to the economy as a whole. Bush, Rubio and Christie basically agree with this view in the proposals that they've produced. Like the flat taxes, these three proposals simplify the tax code and reduce taxes paid by the rich, but they don't change the essential structure of the income tax code. Greater incomes would be taxed at higher average rates. These candidates would maintain or expand credits designed to help the working poor and middle-class families.

[Read more: What's new and what isn't in Jeb Bush's tax plan]

Then there's Trump, who has said he is willing to raise taxes on the rich. Trump has not put forward a detailed plan explaining how he'd do so.