“I’ve made my decision,” Obama said in an email to supporters early Wednesday.

Obama planned to introduce his pick at 11 a.m. in the White House Rose Garden, setting up a showdown with Senate Republicans who have told the White House not to bother filling the vacancy in an election year.

In his email, Obama did not identify his choice to replace the Scalia on the nine-member court. But the president said he had devoted a “considerable amount of time and deliberation to this decision” and consulted with outside experts and groups.

“In putting forward a nominee today, I am fulfilling my constitutional duty. I’m doing my job,” Obama wrote. “I hope that our senators will do their jobs, and move quickly to consider my nominee.”

That will be a hard sell because 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.

The Associated Press has reported that Obama had narrowed the list to three appeals court judges: Merrick Garland, the chief judge of the appeals courts in Washington, D.C.; Sri Srinivasan, a judge on that court; and Paul Watford of the appeals courts based in San Francisco.

In his email, Obama said his nominee will be “eminently qualified” to sit on the nation’s highest court. He said the nominee would understand the limits of the judiciary’s role and “grasps the way it affects the daily reality of people’s lives in a big, complicated democracy, and in rapidly changing times.”

Obama said the White House had “reached out to every member of the Senate, who each have a responsibility to do their job and take this nomination just as seriously.”

The president told supporters that his nominee “deserves a fair hearing, and an up-or-down vote.”