With a two-paragraph letter, Supreme Court Justice Anthony M. Kennedy sent a shock to the Senate’s agenda — and perhaps the 2018 midterm elections.

Senate Majority Whip John Cornyn said the debate over President Donald Trump’s nominee to replace Kennedy, who announced his retirement Wednesday, will likely lead the headlines heading into November.

“I think that it will provide a lot of energy on both sides,” the Texas Republican said. “It may become the most important [issue] because people are seeing the difference it makes.”

That’s even if Kennedy’s retirement was not entirely surprising.

Watch: Decoding the High Court Confirmation Process — 2 Things Trump Needs to Worry About

The senators in the middle will again be in focus, led by Republicans Susan Collins of Maine and Lisa Murkowski of Alaska, along with the many Democrats on the November ballot running in states won by Trump.

Collins told a group of reporters Wednesday that she believes Roe v. Wade, the landmark Supreme Court abortion rights decision, should be considered settled law. But she told a separate group it would be premature to comment otherwise.

“At this point, I have absolutely no idea who the next nominee is going to be, so it’s impossible for me to have concerns when I don’t know who it’s going to be,” she said.

West Virginia Sen. Joe Manchin III, who was the first Senate Democrat to announce support for Neil Gorsuch ahead of his Supreme Court confirmation last year, will also be a target. He faces a tough race against state Attorney General Patrick Morrisey in a state Trump won by 42 points in 2016.

“I look forward to meeting with and evaluating the qualifications of whoever President Trump nominates to become a justice on the Supreme Court,” Manchin said in a statement. “Senators have a responsibility to do our jobs as elected officials and this includes our Constitutional obligation to advise and consent on a nominee to fill this Supreme Court vacancy.”

No 2016 redux

Many Democrats were pushing for Senate Majority Leader Mitch McConnell to delay consideration of a nominee until after the midterm elections, citing his refusal to hold a hearing for Merrick Garland, who was nominated by President Barack Obama in 2016 to fill the seat of the late Antonin Scalia.

“There should be no consideration of a Supreme Court nominee until the American people have a chance to weigh in,” Senate Judiciary ranking Democrat Dianne Feinstein of California said in a statement. “Leader McConnell set that standard in 2016 when he denied Judge Garland a hearing for nearly a year, and the Senate should follow the McConnell Standard.”

In any case, McConnell was quick to announce that a confirmation vote on the next justice will take place this autumn. Even before there was a vacancy, he and other Republicans argued that the rule of not considering a nominee during an election year applied to the last year of a presidential term — although there is no rule on such things outside of what the majority leadership deems so. 

“We will vote to confirm Justice Kennedy’s successor this fall. As in the case of Justice Gorsuch, Senators will have the ‎opportunity to meet with President Trump’s nominee, examine his or her qualifications, and debate the nomination,” the Kentucky Republican said on the floor. “I have every confidence in Chairman [Charles E.] Grassley’s conduct of the upcoming confirmation process in the Judiciary Committee.”

Watch: McConnell Vows Vote on Kennedy Successor ‘This Fall’

If Trump and McConnell can hold the GOP conference in place, not a single Democratic vote would be needed to get a nominee through. That’s because McConnell altered the rules to allow Gorsuch to be confirmed with 50 votes.

“This will be the first, and last, partisan filibuster of a Supreme Court justice,” the majority leader said last year as the Senate prepared to vote on Gorsuch, who has delivered for  conservatives since joining the Supreme Court.

Gorsuch was among 25 potential candidates on a list developed by Trump with the assistance of conservatives who support a so-called strict constructionist judicial philosophy.

And a comment Trump made Wednesday all but ensures that a fight is coming over a nominee who could alter the balance of the court for the next several decades.

“It will be somebody from that list,” the president told reporters in the Oval Office. “Hopefully, we will pick someone who is just as outstanding” as the retiring Kennedy, he added.

Full steam ahead

Trump signaled his pick will come soon.

Asked if he would consider withholding a Supreme Court nominee until the shape of the new Congress is known in November, Trump replied: “I haven’t really thought about that. I think you want to go as quickly as possible.”

Senate Republicans who have been the most critical of Trump on policy matters probably will not be obstacles to a speedy confirmation process.

Tennessee GOP Sen. Bob Corker, for instance, said he hopes Trump nominates a successor “much like” Gorsuch. He dismissed Democrats’ call to delay consideration of a nomination until after the November elections saying — rather remarkably given how much the issue animates both sides — “I can’t imagine why the midterms would affect timing.”

Collins said likewise about the calendar, though she stressed that she disagreed with McConnell’s tactics in 2016.

“I see no why reason why there should be a delay. I would note that I also felt that Merrick Garland deserved a hearing and consideration,” she said. “So I don’t apply a different standard depending on who happens to be president.”

Cornyn told Roll Call he anticipated the Judiciary Committee, of which he is a member, would be able to hold confirmation hearings for Trump’s nominee during the scheduled August work period. McConnell had already scrapped plans for  a full August recess.

The Senate summer legislative agenda features the farm bill on the floor this week, as well as further packages of spending legislation, and a reauthorization of water infrastructure projects and the Federal Aviation Administration. Cornyn said he thought much of that agenda would not need to be derailed.

“I think it becomes the No. 1 priority, but we’ve got plenty to do … while the committee is doing its work and the background checks are being done,” he said. “Hopefully, we can walk, talk and chew gum at the same time.”