Updated

President Obama named federal appeals judge Merrick Garland on Wednesday as his pick to succeed Antonin Scalia on the U.S. Supreme Court – setting up a showdown with Republicans who have vowed to block the choice.

Obama, who said he went through a rigorous and comprehensive screening process, said Garland would bring “integrity, modesty and an even-handedness” to the Supreme Court.

“I said I would take this process seriously, and I did,” Obama said at the Rose Garden ceremony.

Yet within minutes, Republicans doubled down on their opposition to confirming any nominee in an election year, insisting that the vacant seat not be filled until a new president is sworn in.

“It is a president’s constitutional right to nominate a Supreme Court justice and it is the Senate’s constitutional right to act as a check on a president and withhold its consent,” Senate Majority Leader Mitch McConnell said on the Senate floor.

Obama, anticipating the swift resistance, urged Republicans to reconsider, adding it would be unprecedented for Garland not to at least get a hearing.

“I hope they’re fair. That’s all,” Obama said. “To give him a fair hearing and up or down vote.”

Obama said earlier Wednesday that it was both his “constitutional duty to nominate a justice and one of the most important decisions that I – or any president – will make.”

He added, “I’m doing my job. I hope that our senators will do their jobs, and move quickly to consider my nominee.”

A Senate confirmation is required for any nominee to join the bench.

Before the announcement, Sen. Mike Lee, R-Utah, also told Fox News that neither he nor his GOP colleagues on the Senate Judiciary Committee would back down and declared once more he would stop the nomination from going forward.

Data curated by InsideGov

“We’ve been clear,” Lee said of his plan to reject Garland’s nomination.

Garland has served under both Republicans and Democrats. He clerked for the court’s liberal icon, Justice William J. Brennan Jr. In 1997, 32 Republicans voted in favor of his nomination, including seven who are still members of the Senate.

Garland was mentioned as a possible nominee when Justice Paul Stevens retired in 2010.

The vacancy ultimately went to Justice Elena Kagan.

Sen. Chuck Schumer of New York, the No. 3 Democratic leader, called Garland's section, "a bipartisan choice," adding: "If the Republicans can't support him, who can they support?"

Senate Minority Leader Harry Reid, who spoke to Obama Wednesday morning, said in brief remarks on the Senate floor that Republicans must act on the president's choice. "He's doing his job this morning, they should do theirs," said the Nevada Democrat.

If confirmed, Garland would be expected to align with the more liberal members, but he is not viewed as down-the-line liberal. Particularly on criminal defense and national security cases, he's earned a reputation as centrist, and one of the few Democratic-appointed judges Republicans might have fast-tracked to confirmation -- under other circumstances.

But in the current climate, Garland remains a tough sell. Republicans control the Senate, which must confirm any nominee, and GOP leaders want to leave the choice to the next president, denying Obama a chance to alter the ideological balance of the court before he leaves office next January. Republicans contend that a confirmation fight in an election year would be too politicized.

Ahead of Obama's announcement, the Republican Party set up a task force that will orchestrate attack ads, petitions and media outreach. The aim is to bolster Senate Republicans' strategy of denying consideration of Obama's nominee. The party's chairman, Reince Priebus, described it as the GOP's most comprehensive judicial response effort ever.

On the other side, Obama allies have been drafted to run a Democratic effort that will involve liberal groups that hope an Obama nominee could pull the high court's ideological balance to the left. The effort would target states where activists believe Republicans will feel political heat for opposing hearings once Obama announced his nominee.

For Obama, Garland represents a significant departure from his past two Supreme Court choices. In nominating Sonia Sotomayor and Elena Kagan, the president eagerly seized the chance to broaden the court's diversity and rebalance the overwhelming male institution. Sotomayor was the first Hispanic confirmed to the court, Kagan only the fourth woman.

Garland -- a white, male jurist with an Ivy League pedigree and career spent largely in the upper echelon of the Washington's legal elite -- breaks no barriers. At 63 years old, he would be the oldest Supreme Court nominee since Lewis Powell, who was 64 when he was confirmed in late 1971.

Presidents tend to appoint young judges with the hope they will shape the court's direction for as long as possible.

Those factors had, until now, made Garland something of a perpetual bridesmaid, repeatedly on Obama's Supreme Court lists, but never chosen.

But Garland found his moment at time when Democrats are seeking to apply maximum pressure on Republicans. A key part of their strategy is casting Republicans as knee-jerk obstructionists ready to shoot down a nominee that many in their own ranks once considered a consensus candidate. In 2010, Utah Sen. Orrin Hatch called Garland "terrific" and said he could be confirmed "virtually unanimously."

The White House planned to highlight Hatch's past support, as well as other glowing comments about Garland from conservatives.

A native of Chicago and graduate of Harvard College and Harvard Law School, Garland clerked for two appointees of Republican President Dwight D. Eisenhower -- the liberal U.S. Supreme Court Justice William Brennan Jr. and Judge Henry J. Friendly, for whom Chief Justice John Roberts also clerked.

In 1988, he gave up a plush partner's office in a powerhouse law firms to cut his teeth in criminal cases. As an assistant U.S. attorney, he joined the team prosecuting a Reagan White House aide charged with illegal lobbying and did early work on the drug case against then-D.C. Mayor Marion Barry. He held a top-ranking post in the Justice Department when he was dispatched to Oklahoma City the day after bombing at the federal courthouse to supervise the investigation. The case made his career and his reputation. He oversaw the convictions of Timothy McVeigh and Terry Nichols, and went on to supervise the investigation into Unabomber Ted Kaczynski.

President Bill Clinton first nominated him to the D.C. Circuit in 1995.

His prolonged confirmation process may prove to have prepared him for the one ahead. Garland waited 2 1/2 years to win confirmation to the appeals court. Then, as now, one of the man blocking path was Iowa Sen. Charles Grassley, argued he had no quarrel with Garland's credentials, but a beef with the notion of a Democratic president trying to fill a court he argued had too many seats.

Grassley ultimately relented, although he was not one of the 32 Republicans who voted in favor of Garland's confirmation. Nor was Sen. Mitch McConnell, the other major hurdle for Garland now. The Republicans who voted in favor of confirmation are Sen. Dan Coats, Sen. Thad Cochran, Sen. Susan Collins, Sen. Orrin Hatch, Sen. Jim Inhofe, Sen. John McCain, and Sen. Pat Roberts.

The Associated Press contributed to this report.