Senate Majority Leader Mitch McConnell of Ky. on Capitol Hill in Washington in early February. (AP Photo/J. Scott Applewhite) (J. Scott Applewhite/AP)

Majority Leader Mitch McConnell took a victory lap in December, declaring that his first year in charge of the Senate brought the chamber back to its venerable tradition of free-flowing debate, breaking a spell of dysfunction.

“By any objective standard, I think the Senate is clearly back to work,” the Kentucky Republican declared at a year-end news conference.

Now, barely six weeks into the new year, McConnell’s biggest declaration is about not letting the Senate work. About two hours after Supreme Court Justice Antonin Scalia’s death was made public, McConnell issued a statement declaring that the Senate would not consider a replacement to succeed him so that the voters in November could “have a voice in the selection” by picking a new president to make the choice.

By any objective standard, it’s a high-risk move by McConnell, whose own majority could be at stake with seven GOP-held seats in peril in November. From President Obama to Senate leaders, Democrats have begun to accuse McConnell of preventing senators from doing one of their most solemn duties in considering who should serve on the highest court in the land.

Such a refusal would set up the potential for the November elections to become far more consequential than they already appeared. Voters will be deciding the next president and, therefore, who gets to decide the ideological balance of the Supreme Court, as well as determining which party controls the Senate and gets to decide whether to confirm that nominee to the court. The late justice has long been considered the ideological leader of the court’s conservative flank, making the Scalia succession even more important to Republicans who viewed his writings as the foundation of constitutional thinking.

“Let them stand up and tell the American people they won’t be responsible,” said Sen. Patrick J. Leahy (D-Vt.), the ranking minority-party member of the Judiciary Committee. Leahy, who is also the most senior senator, said McConnell should at least let the committee vet the nominee and then have a full vote on whether to confirm the selection, suggesting it will become a major issue for control of the Senate next year.

“That would be reason enough to help the voters make up their minds in Senate races,” he said.

For now, McConnell is standing pat. By Sunday afternoon, aides reported that there had been no calls between Obama and McConnell, or any other senior administration officials, not even Vice President Biden, who has the closest relationship with McConnell of any White House official.

McConnell’s allies agree that they should not let a president in his final months in office make a lifetime appointment to the court that will likely flip the ideological balance for perhaps a generation to come.

Leahy’s counterpart, Sen. Charles E. Grassley (R-Iowa), the Judiciary chairman, called it “standard practice” over the past 80 years to not nominate and confirm Supreme Court justices during a presidential election year. He added that Obama’s use of executive actions that end up battled out in the federal courts added to the rationale for not considering an appointment until the new president takes office.

“It only makes sense that we defer to the American people who will elect a new president to select the next Supreme Court justice,” Grassley said in a statement.

The election-year record, however, is actually contradictory on whether to confirm nominees then, and it has rarely been an issue. In February 1988, on a unanimous 97-to-0 vote, the Senate confirmed Justice Anthony M. Kennedy in the final year of Ronald Reagan’s presidency, an opening that occurred in mid-1987.

The only time since World War II that an opening occurred during a presidential election year was in 1968, when the outgoing president, Lyndon B. Johnson, nominated Justice Abe Fortas to succeed retiring Chief Justice Earl Warren. Fortas withdrew after the Senate blocked him on a first ballot just weeks before the election.

Bucking up McConnell, politically, are the Republican presidential candidates, each of whom Saturday night at a debate in South Carolina called for the seat to remain vacant until one of them has squared off with the Democratic nominee in the general election.

Even House Republicans in potential swing districts issued proclamations that Obama should not get to fill the vacancy.

“The next president must nominate a justice who will continue Justice Scalia’s unwavering commitment to the founding principles,” said Rep. Barbara Comstock (R-Va.), whose Northern Virginia district Democrats have targeted.

What remains to be seen is whether Republican incumbents facing difficult elections can withstand the pressure from their opponents to not even give the Obama selection a full hearing and vote.

Former Ohio governor Ted Strickland, the probable Democratic challenger to Sen. Rob Portman (R-Ohio), was delivering a speech Saturday in Cleveland before the news of Scalia’s death on the importance of preventing the court from being “further radicalized” with conservative justices.

Now, Strickland said in an interview Sunday, “I intend to continue to talk about this until the polls close.”

His line of attack against Portman is going to be over whether the incumbent will abdicate any consideration of the selection to replace Scalia: “Senator Portman, who has your allegiance, your country or your party leaders?”

Portman has so far declined to comment on the process or politics of the succession, only praising Scalia as one of the “preeminent Supreme Court justices of our time.”

One potential move by McConnell and Grassley would be to allow the nomination to go forward all the way to a confirmation vote on the Senate floor, knowing that the odds of any Obama selection winning are negligible. Such a move would allow endangered incumbents such as Portman and Sens. Patrick J. Toomey (R-Pa.) and Kelly Ayotte (R-N.H.) to tell their constituents they performed their duty.

Obama’s first two choices for the court, Justices Sonia Sotomayor and Elena Kagan, were relatively free of controversy and were replacing members of the court’s liberal wing, so there was no ideological shift in the balance. Despite that, just nine Republicans voted for Sotomayor and just five voted for Kagan.

Of those five Republicans, only Sen. Susan Collins (R-Maine) and Lindsey O. Graham (R-S.C.) remain in office. Graham has already indicated that he does not want to let Obama fill the vacancy, making it an uphill challenge to win a simple majority to get a nominee confirmed. Even if he could find a half-dozen Republican votes, Obama would probably need 60 votes to clear a near-certain filibuster by Senate conservatives.

The Democratic caucus has 46 members, meaning Obama would somehow need to find 14 Republican votes to end a filibuster — a tally that would be nearly impossible under the best of circumstances.

Strickland said that Republicans could not hold the seat hostage because they do not like the current occupant of the Oval Office. “The people have spoken, on two occasions,” he said, referring to Obama’s 2008 and 2012 victories.

“It is pure raw politics, and when it comes to the court, we have a higher duty,” he said.