WASHINGTON — Thirteen months into his presidency, Barack Obama finally gave liberal supporters the kind of judicial nominee they had sought and conservatives feared.

Goodwin Liu, 39, is an unabashed liberal legal scholar who, if confirmed, could become a force on the federal appeals court for decades. There’s talk that in time, the Rhodes Scholar, former high court clerk and current assistant dean and law professor at the University of California, Berkeley, could be the first person of Asian descent chosen for the Supreme Court.

“I can easily imagine him” as a high court nominee, said Erwin Chemerinsky, a Liu supporter and dean of the law school at the University of California, Irvine.

Obama’s choice of Liu for the 9th U.S. Circuit Court of Appeals in San Francisco drew quick and vociferous criticism from conservatives. Sen. Jeff Sessions of Alabama, the senior Republican on the Senate Judiciary Committee, described Liu as “far outside the mainstream of American jurisprudence.”

For the first time, Obama seemed to be taking a page from the playbook of recent Republican presidents who nominated conservatives in their 30s and 40s with the expectation they would have enduring influence in setting policy on the federal bench.

Whether a string of younger, more ideological nominees will follow from the Democratic president is unknown. Of the four Obama nominees announced since Liu’s selection on Feb. 24, three are their 50s and the other is a 45-year-old career prosecutor.

The payoff of the approach taken by President Ronald Reagan is evident today. Young judges appointed to the bench in the mid-1980s remain powerful forces on appeal courts in Chicago, Cincinnati, Richmond, Va., and San Francisco.

In an era when appeals court experience is virtually a prerequisite for the Supreme Court, five of the nine justices became appeals court judges before they were 45. Chief Justice John Roberts and Justice Anthony Kennedy were nominated to appellate judgeships before they turned 40, though Senate Democrats blocked Roberts’ nomination near the end of George H.W. Bush’s presidency.

First, though, Liu has to overcome anticipated Republican stalling tactics to win Senate confirmation.

Only six of Obama’s 15 appeals court nominees have been confirmed even though the president’s choices have seemed designed to avoid “high-profile fights,” in the words of Curt Levey of the conservative Committee for Justice.

Nan Aron, president of the liberal Alliance For Justice, agreed that Obama has mainly chosen moderate federal trial judges for appeals courts.

“Unlike Reagan and the recent Bush, he certainly has not made ideology the hallmark of his judicial selection program,” Aron said.

Seventeen Reagan nominees took their appeals court seats before they were 45, but the president did not immediately reach out to younger choices. The pace of those appointments quickened later in Reagan’s first term, and especially, at the start of his second.

If there is a hallmark to Obama’s choices to date, it is diversity, former Obama White House counsel Gregory Craig said. Obama has nominated five women, five African-Americans, two Asian-Americans and a Hispanic among his appeals court choices.

White House officials said the president is filling vacancies on courts with heavy workloads or seats that have been open for years, in some cases. They noted that Obama nominated 32 judges in 2009 and already has sent 19 names to the Senate this year, with a steady stream of selections expected in the coming months.

But Heather Gerken, a Yale law professor and former law clerk to Justice David Souter, said she believes concerns about judicial salaries — lower than at private firms and top-notch law schools — and the threat of unpleasant confirmation hearings could complicate the search for judicial nominees.

“I think it’s harder to find Goodwin Lius nowadays than it used to be,” Gerken said. “People are less willing to give up great careers elsewhere to go on the judiciary at a young age.”

If a fight over Liu’s nomination emerges in the Senate, Republicans will label him a liberal judicial activist, while Democrats will defend Liu as a moderate committed to core constitutional values.

They will talk about his impact on the 9th Circuit, but the real focus will be on something else.

“The bigger concern is that he’ll wind up on the Supreme Court,” said Levey, a conservative.

Both parties have done this dance before. Democrats charged Republicans with delaying for more than a year Sonia Sotomayor’s confirmation as an appeals court judge in the late 1990s because they saw her — correctly, it turned out — as the high court’s first Hispanic justice. Sotomayor was 43 when President Bill Clinton nominated her to the appeals court. Last May, Obama picked her for the Supreme Court.

Republicans claimed Democrats repaid them in kind after President George W. Bush nominated a leading conservative lawyer and a Hispanic, Miguel Estrada, to the appeals court in Washington in 2001. Estrada was 39 when nominated and three weeks shy of his 41st birthday when he withdrew his nomination after waiting more than two years.