WASHINGTON (Reuters) - President Donald Trump nominated Brett Kavanaugh for the U.S. Supreme Court on Monday as he aimed to entrench its conservative control for years to come, but the federal appeals court judge faces a tough confirmation fight in the bitterly divided Senate.

While some Democrats promised a stern effort to block the 53-year-old Kavanaugh - who has served 12 years on the most influential U.S. appeals court - Trump’s fellow Republicans control the Senate by a narrow margin and can ensure confirmation if they avoid defections from their ranks.

If confirmed, Kavanaugh would replace long-serving conservative Justice Anthony Kennedy, who announced his retirement on June 27 at age 81. Kavanaugh became Trump’s second lifetime appointment to the nation’s highest judicial body in his 18 months in office.

Kavanaugh is a well-known figure in Washington and has been involved in some of the biggest controversies of the past two decades. He helped investigate Democratic former President Bill Clinton in the 1990s working for independent counsel Kenneth Starr. He was on Republican George W. Bush’s team in the contentious Florida recount fight in the 2000 presidential election, then served as a senior official in Bush’s White House.

“Throughout legal circles he’s considered a judge’s judge, a true thought leader among his peers,” Trump, who named conservative Justice Neil Gorsuch to the court last year, told an applauding audience in the White House East Room.

“He’s a brilliant jurist with a clear and effective writing style, universally regarded as one of the finest and sharpest legal minds of our time. And just like Justice Gorsuch, he excelled as a legal clerk for Justice Kennedy,” Trump added, saying Kavanaugh “deserves a swift confirmation and robust bipartisan support.”

The appointment will not change the ideological breakdown of a court that already has a 5-4 conservative majority, but nevertheless could move the court to the right. Kennedy sometimes joined the liberal justices on key rulings on divisive social issues like abortion and gay rights, a practice his replacement may not duplicate.

Kavanaugh has amassed a solidly conservative judicial record since 2006 on the influential U.S. Court of Appeals for the District of Columbia Circuit, the same court where three current justices including Chief Justice John Roberts previously served. Some conservative activists have questioned whether he would rule sufficiently aggressively as a justice.

Like the 50-year-old Gorsuch, Kavanaugh potentially could serve on the high court for decades. Trump’s other leading candidates for the post were fellow federal appellate judges Thomas Hardiman, Raymond Kethledge and Amy Coney Barrett.

“My judicial philosophy is straightforward: a judge must be independent and must interpret the law, not make the law. A judge must interpret statutes as written. And a judge must interpret the Constitution as written, informed by history, and tradition and precedent,” Kavanaugh said during the ceremony in which he emphasized his family and his Roman Catholic faith.

Kavanaugh survived a protracted confirmation fight after Bush picked nominated him to the appeals court in 2003. Some Democrats accused him of excessive partisanship, and it took three years before the Senate eventually voted to confirm him.

Republicans hold a slim 51-49 Senate majority, and with ailing Senator John McCain battling cancer in his home state of Arizona they currently can muster only 50 votes. Senate rules still leave Democrats with scant options to block confirmation by themselves, though Trump must prevent Republican defections.

Moderate Republican Senators Susan Collins and Lisa Murkowski said they could carefully vet Kavanaugh before deciding how to vote. Democratic senators serving in Republican-leaning states including Joe Manchin of West Virginia, Joe Donnelly of Indiana and Heidi Heitkamp of North Dakota made similar remarks, though top Senate Democrat Chuck Schumer blasted Trump’s pick.

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‘RIGHTS AND FREEDOMS’

“In selecting Judge Brett Kavanaugh for the Supreme Court, President Trump has put reproductive rights and freedoms and healthcare protections for millions of Americans on the judicial chopping block,” Schumer said.

Senate Majority Leader Mitch McConnell, who earlier in the day accused the “far left” of “scare tactics” to try to thwart the nomination, called Kavanaugh “a superb choice.”

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A White House official, speaking on condition of anonymity, said Kavanaugh was informed on Sunday night he would be the nominee, adding that “what really tipped the scales was the consistency” the judge had shown on the appeals court. The official said the White House reached out to every member of the Senate Judiciary Committee, which will hold confirmation hearings, and that only Democrat Kamala Harris “refused to engage.”

Trump last year appointed Gorsuch, who has already become one of the most conservative justices, after Senate Republicans in 2016 refused to consider Democratic former President Barack Obama’s nominee Merrick Garland to fill a vacancy left by the death of conservative Justice Antonin Scalia. As a result, Democrats have accused Republicans of stealing a Supreme Court seat. Gorsuch restored the court’s conservative majority.

Kavanaugh worked for Starr, whose investigation of Clinton helped spur an effort by congressional Republicans in 1998 and 1999 to impeach the Democratic president and remove him from office. Kavanaugh in 2009 changed his tune on the Starr probe, arguing that presidents should be free from civil lawsuits, criminal prosecutions and investigations while in office.

Trump defeated Clinton’s wife, Hillary Clinton, in the 2016 presidential election and has disparaged both Clintons.

Democrats in the past also have pointed to Kavanaugh’s work for Bush during the 2000 recount fight, a controversy that was resolved only after the conservative-majority Supreme Court sided with Bush over Democratic candidate Al Gore, settling the election outcome.

The new justice can be expected to cast crucial votes on other matters of national importance including gay rights, gun control, the death penalty and voting rights. The court could also be called upon to render judgment on issues of personal significance to Trump and his administration including matters arising from Special Counsel Robert Mueller’s ongoing Russia-related investigation and several civil lawsuits pending against Trump.