WASHINGTON — President Barack Obama sought Wednesday to reshape the clash over presidential power that has engulfed the vacancy on the Supreme Court by nominating a federal judge with a centrist reputation, Merrick Garland, and all but daring Republicans to hold fast to their refusal to consider his choice.

Obama held up his pick of the 63-year-old Garland as an opportunity for Republicans to reverse course and avoid making the judicial system “an extension of our divided politics.”

“I said I would take this process seriously — and I did,” Obama said as he stood alongside Garland, the chief judge of the U.S. Court of Appeals for the District of Columbia Circuit. “At a time when our politics are so polarized, at a time when norms and customs of political rhetoric and courtesy and comity are so often treated like they're disposable — this is precisely the time when we should play it straight.”

The president's Rose Garden announcement amounted to a political challenge to Republicans just as they appear to be grappling with the consequences of their own stalwart opposition to Obama throughout his presidency with the surprising rise of GOP presidential front-runner Donald Trump.

Obama praised Garland as the kind of candidate he had promised to choose: one with sterling credentials and a widely respected temperament.

Garland is “one of America's sharpest legal minds,” who “brings to his work a spirit of decency, modesty, integrity, even-handedness and excellence,” Obama said.

“GOP leaders, though, held firm to the position they first claimed just hours after the death last month of Justice Antonin Scalia: that they wouldn't even meet with the nominee, insisting Obama doesn't have the mandate so close to the end of his term to be making such a consequential move, and preferring instead to leave the choice to Obama's successor.

“It's about a principle and not a person,” Senate Majority Leader Mitch McConnell, R-Ky., said on the floor of the Senate moments after Obama and Garland left the Rose Garden. “It seems President Obama made this nomination not with the intent of seeing a nominee confirmed, but in order to politicize it for the purposes of the election.”

White House officials insisted Obama's choice was driven by a desire to pick the most qualified candidate, unaffected by the politics of an election year that supported McConnell's pledge. “It's fair to say that there's simply nobody better qualified,” said White House counsel Neil Eggleston, who helped lead the vetting process.

Garland, who lives in Bethesda, spoke with Sens. Barbara A. Mikulski and Ben Cardin by phone on Wednesday. Both Maryland Democrats used the nomination to reiterate their call for Senate Republicans to schedule a confirmation hearing that appeared unlikely to materialize.

“The Senate must perform its duty and do our jobs as mandated by the Constitution,” Mikulski said in a statement. “Let's hold a vote on the Senate floor.”

Cardin – who attended Obama's announcement at the White House – agreed. “It is now necessary for the Senate to fulfill its constitutional responsibility to consider the nomination through a fair hearing and a thoughtful floor debate before a timely vote of the full Senate.”

Rep. Andy Harris, the state's sole Republican in Congress, offered the view that was shared by most Republicans on Capitol Hill. “Once again President Obama is playing politics with the future of this country by attempting to force the Senate to confirm a liberal Washington insider to the Supreme Court,” the Baltimore County lawmaker said.

Several longtime GOP members of the Senate Judiciary Committee have publicly lobbied for Garland's selection in the past. Seven current Republican senators voted to confirm Garland to the federal bench in 1997.

White House officials believe they stand a chance of getting a confirmation hearing for Garland in the Senate despite McConnell's opposition and pointed to some Republicans appearing to break ranks by opening the door to at least meeting with Garland.

The White House lobbying effort began as soon as Garland left the Rose Garden. He started calling senators and will go to Capitol Hill to meet them — at least those willing to invite him in — on Thursday.

Obama's announcement came a day after he challenged politicians in both parties to examine what role they played in helping to give rise to a “vicious atmosphere in our politics.”

He seemed to be appealing to GOP senators who have tried to distance themselves from Trump amid concerns that his inflammatory rhetoric could hurt their own chances for re-election and cost the party its control of the Senate.