WASHINGTON -- Supreme Court nominee Brett Kavanaugh's past writings a president should not be distracted by lawsuits and investigations could become a flashpoint in what's already shaping up to be a contentious confirmation battle.

With special counsel Robert Mueller investigating whether President Donald Trump obstructed justice, questions about whether a chief executive can be subpoenaed or indicted could potentially reach the Supreme Court. Though there's no indication at this point it will happen, it's sure to be a major topic of questioning at Kavanaugh's confirmation hearing as the Senate weighs whether to confirm him to replace retiring Justice Anthony Kennedy.

Democrats opposing Kavanaugh are already weighing in, saying the past writings -- particularly a legal article he wrote on the separation of powers in 2009 -- suggest he would be inclined to side with Trump.

Senate Democratic leader Chuck Schumer said Tuesday he "seems exactly like the kind of man President Trump would want on the Supreme Court if legal issues from the Mueller probe arise."

Kavanaugh was a key player in the investigation leading to President Bill Clinton's impeachment, but a decade later he wrote the experience, coupled with his time working for President George W. Bush, had persuaded him presidents should not have to face criminal investigations, including indictments, or civil lawsuits while they are in office. He said Congress should pass a law temporarily protecting presidents from such distractions in office.

Clinton, for example, "could have focused on Osama bin Laden without being distracted by the Paula Jones sexual harassment case and its criminal investigation offshoots," Kavanaugh wrote in the 2009 Minnesota Law Review article.

If applied on the court somehow, those opinions could have a direct impact on Trump, who has also been dogged by allegations of sexual harassment.

In the Russia probe, it's theoretically possible the court could have to weigh in on the question of whether a president is immune from criminal prosecution. The Justice Department's Office of Legal Counsel, which provides guidance to executive branch agencies, has said sitting presidents cannot be prosecuted while in office.

In addition to indictment, another issue tied to the Mueller investigation not fully resolved in the courts is whether a sitting president must respond to a subpoena from investigators.

In the 2009 article, Kavanaugh wrote Congress should also exempt the president from questioning by criminal prosecutors or defense counsel.

"Even the lesser burdens of a criminal investigation, including preparing for questioning by criminal investigators, are time-consuming and distracting," he wrote, adding a president concerned about an ongoing criminal investigation "is almost inevitably going to do a worse job as president."

Mueller hasn't indicated he will move to subpoena the president, though his team raised the prospect with Trump's legal team in March and may do so if the president's lawyers refuse to make Trump available for an interview.

Clinton was subpoenaed in 1998 during the independent counsel's Whitewater investigation, though the subpoena was later withdrawn when Clinton agreed to voluntarily testify before the grand jury.

The Supreme Court has never definitively ruled on the question of whether a president can be forced to testify, though the justices in 1974 did rule President Richard Nixon had to produce recordings and documents that had been subpoenaed.

Trump has repeatedly criticized Mueller and the investigation on Twitter, raising concerns in Congress he will move to fire the special counsel. The White House has asserted Trump has the authority to fire Mueller, but only Deputy Attorney General Rod Rosenstein has the power to fire him under current regulations. Rosenstein appointed Mueller in May 2017 after Trump fired FBI Director James Comey.

In a 1998 article in the Georgetown Law Journal, Kavanaugh wrote Congress should give the president the ability to fire special counsels, an opinion Democrats have highlighted in the hours since he was nominated Monday evening.

Kavanaugh's reasoning, however, was not to protect presidents but to make them more accountable. He wrote presidents can complain independent counsels are politically motivated while implying they are powerless to do anything about it. Giving the president firing power would "force the president and his surrogates to put up or shut up."

Noting Nixon's resignation after firing Justice Department officials, Kavanaugh wrote "history clearly demonstrates that the president will pay an enormous political price if he does not have a persuasive justification for dismissing a special counsel."

Harvard Law professor Noah Feldman, who specializes in constitutional studies, on Tuesday warned Democrats not to overstate or misinterpret Kavanaugh's words. He argued because Kavanaugh is suggesting Congress make new laws to exempt presidents from investigations or lawsuits, it's not the same thing as saying the courts should step in. Feldman suggested Kavanaugh could even be implying a president can be indicted, since he believes there should be a law preventing it.

"It's a mistake for Democrats to make this their main line of criticism," Feldman said.

Democrats showed little sign of heeding such advice Tuesday.

Sen. Cory Booker, D-N.J., said the Senate shouldn't consider Kavanaugh's nomination until the Mueller probe is finished.

"The president of the United States should not be beyond criminal investigations," Booker said.

But South Dakota Sen. John Thune, the Senate's No. 3 Republican, chalked the opposition up to "Democrat paranoia."

"It's part of their obsession with Russia, and the president," Thune said, noting Kavanaugh wrote the article proposing presidential exemptions from lawsuits and investigations when President Barack Obama was in office.