President Donald Trump has nominated circuit court judge Neil Gorsuch to fill the vacant seat on the US Supreme Court, setting up a showdown with congressional Democrats and activists over a pick that could shape the ideological bent of the court for a generation.

Gorsuch, 49, the youngest supreme court nominee in 25 years, was among a group of federal judges reported in recent weeks to be on Trump’s shortlist. A strict adherent of judicial restraint known for sharply-written opinions and bedrock conservative views, Gorsuch, a Colorado native, is popular among his peers and is seen as having strong backing among Republicans generally.

The nomination landed at a moment of sharply-increasing alarm amongst progressives that the Trump administration plans to pursue extremist policies on core questions likely to come before the court, from religious equality to abortion rights, voting rights, access to healthcare, LGBT rights, anti-discrimination protections and more.

Announcing his pick in the White House’s East Room, Trump described reading Gorsuch’s writings “closely”, as Gorsuch stood next to Trump listening with a fixed expression of earnest concern, holding his wife, Louise, in one arm.

“I can only hope that both Democrats and Republicans can come together for once for the good of the country,” Trump said.

Some prominent Senate Democrats immediately denounced Gorsuch as “unacceptable” and “extreme”. But it was unclear if there would be sufficient support to mount a filibuster and force an historic showdown over the nomination and Senate procedure.

If Democrats refuse to support Gorsuch, Republicans could decide to change the Senate rules to confirm him. But many Republicans are wary of this move, and are hopeful vulnerable Democrats will come around.

Many Democrats are particularly bitter about the confirmation process after Republicans’ refusal last year to consider the nomination of circuit court judge Merrick Garland, Obama’s selection to replace Scalia. Senate majority leader Mitch McConnell argued at the time that it would be inappropriate for a departing president – 11 months remained in Obama’s term – to make such a significant and long-term appointment.

Trump’s nominee has the potential to tip the court one way or the other on important questions. If confirmed, Gorsuch would return the court to nine justices, filling a seat left vacant since the death of Justice Antonin Scalia in February 2016.

Working for the last year with an even number of justices, the court issued split 4-4 decisions on high-stakes questions such as the protection of undocumented immigrants and the health of public unions, leaving lower court rulings in place.

The next justice to be confirmed may break such ties, giving new strength to the court’s conservative bloc, which could be further buttressed by future Trump nominations in the case of the retirement or death of a justice. One of the four liberal-leaning justices on the court, Ruth Bader Ginsburg, turns 84 in March. Justice Anthony Kennedy, a centrist on the court who has sometimes split tie votes for the progressive wing, is 80 years old.

Gorsuch’s track record as a judge on the US court of appeals for the 10th circuit does not shed obvious light on how he might rule as a supreme court justice on hot-button topics such as abortion and LGBT rights. He is the author of a book about euthanasia in which he writes, “to act intentionally against life is to suggest that its value rests only on its transient instrumental usefulness for other ends.”

Ideological strands running through Gorsuch’s appeals court rulings would seem likely to endear him to congressional Republicans and Trump’s conservative base. He has shown himself to be solicitous to claims of religious exemptions from the law, to gun rights claims and to the prosecution of death penalty cases.

Under current Senate rules, which require 60 votes for a supreme court confirmation, Gorsuch would need to win the support of multiple Democrats, who count 48 Senate caucus members to the Republicans’ 52.

If the Democrats follow through with a filibuster, however, those rules could change. The previous Democratic leadership of the Senate changed the rules to require fewer votes for the confirmation of most executive nominees, and the current Republican leadership could make an additional change to the rules. McConnell earlier had vowed to confirm Trump’s nominee.