Before the president has even made his announcement, advocacy groups are making clear they will play an important role in the coming fight.
Kavanaugh, 53, was first nominated to the appeals court by President George W. Bush in 2003.
The decision has far-reaching implications for America on everything from abortion to guns to immigration.
Senator Dick Durbin (D-Ill.) questions Barrett on her Catholic faith and whether it would influence her decisions on the federal appeals court in her Senate confirmation hearing, September 6, 2017.
"I was lucky. My mum was a teacher in the 1960s and 1970s, she taught history at two largely African American public high schools in Washington DC, McKinlay Tech and HD Woodson", Judge Kavanaugh said.
With reality television-style suspense, he had kept everyone guessing up until the last moment.
Hardiman, who was runner-up to Neil Gorsuch as the president's Supreme Court pick previous year, made a comeback on Trump's shortlist this weekend in part because of the president's sister, Judge Maryanne Trump Barry, who serves with Hardiman on the U.S. Court of Appeals for the Third Circuit.
"I will oppose the nomination the President will make tonight because it represents a corrupt bargain with the far Right, big corporations, and Washington special interests", said Casey in a statement.
Trump last week spoke with seven candidates, all drawn from a shortlist compiled by the conservative Federalist Society, about the Supreme Court.
"I am grateful to you and I am humbled by your confidence in me". Kavanaugh was appointed to the U.S. Court of Appeals for the D.C. Circuit in May 2006. He had previously worked with independent counsel Kenneth Starr in the investigation of President Bill Clinton, and was involved in the Florida presidential vote recount in 2000.
Kethledge, who was a clerk for Kennedy in 1997-98, has been described as very similar ideologically to Gorsuch. He also comes from the D.C. Circuit, which has produced current Justices Clarence Thomas, John Roberts, and Ruth Bader Ginsburg, as well as the late Justice Antonin Scalia.
In a 2013 law review article, Kavanaugh wrote that after seeing firsthand the many hard duties that a president encounters, he thinks that presidents should operate free from the threat of civil suits, such as the sexual harassment suit that led to President Clinton's impeachment, and that presidents should also be free from criminal investigations. Barrett is a former University of Notre Dame law professor, (and a graduate of the school; Kavanaugh meanwhile received his undergrad and law degrees from Yale).
Kavanaugh potentially could serve on the high court for decades.
His appointment will not change the ideological tilt of a court that already has a 5-4 conservative majority, but he could nevertheless shift the bench further right. But Judge Kavanaugh may not be so accommodating.
"It is my honor and privilege to announce that I will nominate Judge Brett Kavanaugh to the United States Supreme Court".
The front-runner was a front-runner for a reason. In the end, however, the safe pick won out.
President Donald Trump points before boarding Air Force One at Morristown Municipal Airport, in Morristown, N.J., Sunday, July 8, 2018, en route to Washington from Trump National Golf Club in Bedminster, N.J.
Mr Trump is securing a conservative judiciary for a generation.
"FreedomWorks calls upon Majority Leader McConnell to act swiftly and ensure Kavanaugh is confirmed on the Senate floor".
A nominee needs a simple majority of 51 votes to be confirmed. He was succeeded by Republican Jeff Flake in 2012 and is now senior counsel at Covington & Burling, the powerhouse bipartisan law and lobbying firm that boasts not just Kyl but also the likes of former Democratic Rep. Howard Berman of California and former Attorney General Eric Holder.
Before a full vote on the chamber floor, the prospective justice will be grilled by the Senate Judiciary Committee in hearings that can go on for days.
"My judicial philosophy is straightforward", Kavanaugh said.
Republicans would have a cushion if even a few vulnerable Democrats cross party lines to support Trump's nominee.
Kavanaugh's record will come under particular scrutiny for clues as to how he might vote in any future review of Roe v Wade, the landmark 1973 decision that guaranteed a woman's right to an abortion.
All eyes on which senators?
Trump asked senators to unite to bring about a swift confirmation. Joe Donnelly, West Virginia Sen.
All three face gruelling re-election campaigns this year in their conservative states.
Meanwhile, liberal groups are already calling on two moderate Republican senators - Susan Collins of ME and Lisa Murkowski of Alaska - to reject the nominee. But in terms of selecting his nominee, the president said he would not use Roe v. Wade as a litmus test for a nominee.