The Supreme Court has remained a largely unspoken topic on the campaign trail — even though the Court plays a critical function in Americans' lives. (This past June's Affordable Care Act ruling, anyone?)

The next president could very well appoint one or two new justices. And who steps down first could also depend on who's elected.

Mitt Romney hasn't said much about the Supreme Court, apart from expressing disagreement with the Court's ruling on Obamacare. But his website states the candidate would nominate judges "in the mold of" the Court's conservatives — Antonin Scalia, Clarence Thomas, Samuel Alito and Chief Justice John Roberts (the last two of whom a then-Sen. Obama voted against confirming). It also says Romney would like to see Roe v. Wade overturned.

President Obama, of course, has appointed two liberal justices, Elena Kagan and Sonia Sotomayor, the nation's first Hispanic justice. His past remarks indicate a preference for nominees who bring "common sense" and "pragmatism" to the table, who'd blend constitutional analysis with "a sense of what real-world folks are going through."

Legal challenges to such key social issues as same-sex marriage, gun rights, immigration and separation of church and state are likely to be heard by the Supreme Court in the coming years. One justice is all it may take to tip the scale in these cases.

So what exactly have the candidates said, and why hasn't the Supreme Court been a bigger issue? Let's take a look.

Mitt Romney

Romney has spoken out against the president's first-term Supreme Court picks.

In April, Romney told the National Rifle Association that he's opposed to judges "who view the Constitution as living and evolving, not timeless and defining."

"In his first term, we've seen the president try to browbeat the Supreme Court. In a second term, he would remake it," Romney said. "Our freedoms would be in the hands of an Obama Court, not just for four years, but for the next 40. That must not happen."

Romney has occasionally embraced recent Supreme Court decisions. He praised the Court's unanimous January 2012 ruling in a religious liberty case that allowed for a "ministerial exception" to employment discrimination laws. He favorably cited another unanimous March 2012 ruling that made it easier for property owners to challenge compliance orders from the Environmental Protection Agency.

The candidate has been vocal about abortion. In June 2011, Romney wrote that he felt Roe v. Wade was a "misguided ruling that was a result of a small group of activist federal judges legislating from the bench." Early this year, Romney repeated that position, and again in April during an interview with ABC News' Diane Sawyer.

His running mate, Paul Ryan, also touched on the Court's role when it comes to abortion. "We don't think that unelected judges should make this decision; that people, through their elected representatives and reaching a consensus in society through the democratic process, should make this determination," Ryan said in the vice-presidential debate.

As Vice President Joe Biden pointed out during this debate, one of the people heading Romney's panel of advisers on judicial appointments is Robert Bork, a Reagan Supreme Court nominee who failed to win Senate confirmation in 1987 over fears he would vote to strike down a range of issues, including Roe v. Wade.

(Biden, then the Chairman of the Senate Judiciary Committee, helped lead the opposition. The vacancy to which Bork was nominated eventually went to Justice Anthony Kennedy, typically the Court's swing vote.)

On another note, Romney would have a deep bench from which to select judicial nominees, given Republicans' vigorous focus on this area. (CNN has compiled a list of likely nominees, including former U.S. Solicitor General Paul Clement — who argued the Affordable Care Act challenge — and an assortment of conservative federal appellate judges.)

"Romney would appoint people with a more conservative judicial philosophy, who are not transforming the Constitution, not sticking up for the rights of any particular group and are very neutrally interpreting the law," said Curt Levey, president of Committee for Justice, an organization that promotes conservative judicial candidates.

President Obama

If Obama is reelected, there is strong speculation that Justice Ruth Bader Ginsburg, the Court's oldest member at 79, will retire to make room for a replacement. In that event, argue some, the president would likely nominate another woman (two other justices are also approaching their late 70s: Scalia and Kennedy are both 76.)

"[Obama] would place value on racial and ethnic diversity, but it wouldn't be determinative," said Tom Goldstein, co-founder and regular contributor to SCOTUSBlog, which provides news and analysis of the Court's decisions. "President Obama hasn't really pushed for very liberal nominees."

Back in 2008, Obama shed light on his thoughts about the subject.

In remarks to the Detroit Free Press, then-Sen. Obama said he would seek Supreme Court nominees who recognize "that one of the roles of the courts is to protect people who don't have a voice," for instance, "the vulnerable, the minority, the outcast, the person with the unpopular idea, the journalist who is shaking things up."

That same year, Obama, who taught constitutional law at University of Chicago Law School, praised former Justice David Souter and current Justice Stephen Breyer — both considered liberal votes — as "very sensible judges."

"They believe in fidelity to the text of the Constitution, but they also think you have to look at what is going on around you and not just ignore real life," he said.

Obama has made clear he supports Roe v. Wade, which has been narrowed in the face of new challenges.

In 2010, shortly after Justice John Paul Stevens announced his retirement, Obama told Senate lawmakers he'd apply no "litmus test" to potential nominees.

"But I will say that I want somebody who is going to be interpreting our Constitution in a way that takes into account individual rights, and that includes women's rights," the president said, eventually nominating Kagan for the vacancy.

In February 2011, Obama spoke out against the Defense of Marriage Act, which seeks to impose a definition of marriage as a legal union between a man and a woman, and instructed the Justice Department to stop defending the law in court. (A second federal appeals court recently struck down the law as unconstitutional; some predict the issue could next be headed to the Supreme Court.)

Although the president has been criticized for taking his time with judicial appointments in the lower federal courts — a gateway to the Supreme Court — he's also named more ethnic minorities to the bench than any of his predecessors.

More Discussion?

So, why hasn't there been more discussion about the Supreme Court on the campaign trail? It's a question that's been raised again and again, especially since justices, who are appointed for life, serve on average about 30 years.

One possible explanation is that the Supreme Court strategically took itself out of the political calculus earlier this year when it narrowly upheld the health care law.

"[The issue] would have played out a little differently if the Supreme Court had struck down the health care act," SCOTUSBlog's Goldstein said. "It's really hard for the president to run against the Court that has just upheld his signature legislative achievement by a whisker."

But the silence could also just convey a perceived lack of interest among the public.

"I think the candidates realize that the Supreme Court doesn't move independent voters," said Goldstein, even though "the president makes a radical difference in the composition of the judiciary."