The Note: O Brother, Where Art Thou?

— -- NOTABLES

--JEB, GEORGE AND THE POWER OF BROTHERLY LOVE: You don’t see this every day: Former President George W. Bush is hitting the campaign trail in his first public appearance on behalf of his brother Jeb in 2016. The former president has largely avoided politics since leaving the White House, but all of that changes tonight at a joint rally in North Charleston. The Bush brothers will also be joined by former First Lady Laura Bush – a true family affair. “President Bush has been incredibly supportive of his brother’s campaign and Governor Bush is excited to have him out on the trail,” campaign spokeswoman Kristy Campbell said. Campaign aides say thousands are expected to attend, ABC’s CANDACE SMITH notes. The Palmetto State has been good to the family, George H.W. and George W. won each of their respective primaries in the state. http://abcn.ws/1Wn3Gap

--WHAT THE BUSH CAMPAIGN IS SAYING: "We're down to the last weeks, when the eyes on the nation are on South Carolina," said Brett Doster, who heads the campaign's efforts in the state and ran state campaigns for President Bush and Mitt Romney. "The president offered to come in and do some events. The Bush family is extremely well regarded in South Carolina; we will take any family member with the last name Bush at any time."  Doster said that the Palmetto State's large population of veterans sets a perfect stage for the elder Bush to step in. "Military and national defense issues are huge in South Carolina,” he said. “The fact that President has been identified as being strong Commander-in-chief is something we took in consideration.” http://abcn.ws/1Wn3Gap

--TRUMP DOUBLES DOWN ON BUSH FAMILY FEUD: Donald Trump doubled down on the Bush family yesterday on ABC's "This Week." “I think he did a terrible thing when he went into Iraq,” Trump said about former President George W. Bush, ABC’s NICKI ROSSOLL writes. At Saturday's debate in South Carolina, Trump got into a heated exchange with the former Florida governor about his brother's role in the 9/11 attacks. http://abcn.ws/1PUSlhd

--LINDSEY GRAHAM WOULD ‘RE-EVALUATE’ SUPPORTING TRUMP IF NOMINATED: “You know, I’ve got to really re-evaluate that after what he said about President George W. Bush,” South Carolina Sen. Lindsey Graham told ABC’s GEORGE STEPHANOPOULOS on “Good Morning America” today when asked if he would support Trump were he to clinch the Republican presidential nomination. At last weekend’s presidential debate Trump savaged the former president over the war in Iraq and the Sept. 11 terrorist attacks. The mainstream Democratic Party opposition to Bush did not go where Donald Trump went,” Graham said, adding: “That’s something that only comes from the kook part of America.” Graham said “Jeb is definitely surging” and predicted that Trump would not win the GOP nomination. “What he said about President George W. Bush being a liar and that the Bush administration being the cause of 9/11 is Michael Moore stuff,” he said, “So I hope that will bite him a little bit here.”

--ANALYSIS -- ABC’s RICK KLEIN: Justice Scalia’s death sets up an extraordinary, even unprecedented moment for a dysfunctional federal government. A constitutional crisis – starting with a selection process and continuing through an all-but-certain congressional slow-walk to a possible filibuster – will unfurl against the backdrop of a election cycle that will determine the future of all three branches of government. It raises the stakes for the race; the senators on the GOP side joined those calling on President Obama not to make a pick, and Hillary Clinton added a decrying of those Senate vows to her stump. It will be easy enough to lampoon or urge on a broken Washington system over these next few months. The fight over Scalia’s replacement will no doubt galvanize the parties’ respective activist bases. But a wearying fight – with its utterly predictable outcome – won’t necessarily reward the loudest candidate. Given the likeliest of an ugly ride, voters might look to someone who can get things back on course. MORE ON THE WEEKEND THAT CHANGED THE RACE: http://abcn.ws/1QeHzhI

THIS WEEKEND ON THE TRAIL with ABC’s PAOLA CHAVEZ and VERONICA STRACQUALURSI

7 MOMENTS THAT MATTERED AT THE GOP PRESIDENTIAL DEBATE. With the Republican presidential field whittled down to just six candidates, the first presidential debate since the New Hampshire primary and the last one before the Palmetto State’s Feb. 20 nominating contest turned into a rollicking attack-fest that left virtually no contender unscathed. The debate, held at the Peace Center in Greenville, South Carolina, was smorgasbord of sharp volleys that were as often about policy as they were personal. ABC’s SHUSHANNAH WALSHE, VERONICA STRACQUALURSI, CANDACE SMITH, RICK KLEIN and MICHAEL FALCONE highlight at the seven moments that mattered. http://abcn.ws/1QeQ2rm

IN CASE YOU MISSED IT -- THE BEST LINES OF THE DEBATE courtesy of ABC’s PAOLA CHAVEZ http://abcn.ws/243bCDg THE DEBATE IN A MINUTE courtesy of ABC’s TOM THORNTON and ALI DUKAKIS. WATCH: http://abcn.ws/1SO2Be2

CANDIDATES WEIGH IN ON SUPREME COURT VACANCY. The death of U.S. Supreme Court Associate Justice Antonin Scalia at the age of 79 Saturday prompted a moment of silence and the very first question at the debate. Here’s a look at what the candidates said about the vacancy. http://abcn.ws/1QeKCg0

CRUZ PLANS TO FILIBUSTER ANY OBAMA HIGH COURT NOMINEE. Republican presidential candidate Sen. Ted Cruz said on “This Week” that he plans to filibuster any Supreme Court nominee made by President Obama to replace the late Justice Antonin Scalia. Cruz described the Supreme Court vacancy left by Scalia as having a "profound impact" on the Republican primary that will change the contours of the presidential race. He argued voters -- not a "lame-duck president" -- should decide who will replace the longtime conservative judge who died Saturday, ABC’s JESSICA HOPPER reports. "This is a 5-4 court -- the next election needs to be a referendum on the court," Cruz said Sunday. "People need to decide." "This should be a decision for the people," Cruz said. "Let the election decide. If the Democrats want to replace this nominee, they need to win the election.” http://abcn.ws/1QfklOK

CLINTON, SANDERS BLAST REPUBLICANS FOR THREATENING TO BLOCK REPLACEMENT. Bernie Sanders and Hillary Clinton urged President Obama over the weekend to move quickly in making a nomination to the U.S. Supreme Court. They also blasted Republicans on Capitol Hill and on the campaign trail for threatening to block a replacement until after the election. “It appears that some of my Republican colleagues in the Senate have a very interesting view of the Constitution of the United States,” Sanders said in Colorado on Saturday. "Apparently they believe that the Constitution does not allow a Democratic president to bring forth a nominee to replace Justice Scalia. I strongly disagree with that.” Clinton, too, argued Republican lawmakers who want to hold off on an appointment are meddling with the Constitution, calling their efforts “outrageous,” "disappointing,” and “totally out of step with our history and constitutional process.” ABC’s MARYALICE PARKS and LIZ KREUTZ have more. http://abcn.ws/2120ZhP

SANDERS CALLS ON OBAMA TO NOMINATE SCALIA REPLACEMENT ‘AS SOON AS POSSIBLE.’ “President Obama, in my view, should make that nomination,” Sanders said on ABC's “This Week.” “I hope he does it as soon as possible and I hope that the Senate confirms and begins deliberations as soon as possible.” Sanders said he had one litmus test for anyone he would potentially nominate to serve on the Supreme Court: That the new justice would overturn the Citizens United decision, in which the Supreme Court ruled corporations or unions could spend unlimited amounts of money to support or denounce candidates in elections. http://abcn.ws/1Wl67dm

KASICH PUTS HIMSELF IN OBAMA’S SHOES. Republican presidential candidate Gov. John Kasich said Sunday he does not think President Obama should nominate someone to the Supreme Court following Associate Justice Antonin Scalia’s death, but admitted that if he were president he would select a nominee. "Of course I would send somebody," the Ohio governor said on ABC's "This Week with George Stephanopoulos." "But it would probably be a different situation." ABC’s BEN GITTLESON has more. http://abcn.ws/1TgY6XO

RUBIO CALLS REPUBLICAN-ON-REPUBLICAN ATTACKS A ‘CATCH 22.’ Florida Sen. Marco Rubio doesn't believe the constant attacks between those running for the Republican presidential nomination is helping the party. “It’s a catch-22,” Rubio said Sunday on ABC’s "This Week." "But if you're attacked, I think it's important to respond." Rubio said responding to those attacks hurt him a week ago during the last debate before the New Hampshire primary. Rubio has since said that he was trying to avoid Republican-on-Republican attacks and instead wanted to refocus the conversation on President Obama, ABC’s INES DELACUETARA notes. “I’ve said that before -- I always tried to avoid that engagement,” Rubio said Sunday. "It got me in trouble a week ago." http://abcn.ws/1mAyRCU

IN CASE YOU MISSED IT

CLINTON, SANDERS GO TO CHURCH IN VEGAS. Just one week ahead of the Nevada caucuses, the next contest in the fight for the Democratic nomination, Hillary Clinton and Bernie Sanders attended the same African-American church in West Las Vegas -- an unexpected run-in that gave evidence of just how intense the battle for votes between the two of them has become. ABC’s MARYALICE PARKS and LIZ KREUTZ note. The two candidates sat on opposite sides of the packed church, both in the front row, and each listened as the other addressed the crowd. Rep. John Lewis accompanied Clinton. http://abcn.ws/1PLu2Px

WHO’S TWEETING?

@TheBradMielke: Two SC towns to watch tomorrow: Florence, where Rubio &Cruz will hold events, and the Charleston area, where Trump speaks ahead of Jeb & W.

@JHoganGidley: When analyzing the impact of Presidential Debates, keep in mind: you can't win the nomination in a single debate, but you can sure lose it.

@AaronBlake: Donald Trump has a point when he says debate audiences are out to get him http://wpo.st/w4zB1 

‏@tackettdc: Mitch McConnell’s steady Senate headed toward partisan warfare @jestei http://nyti.ms/1ohDeUZ 

@pewresearch: On #PresidentsDay, a look at the religious affiliations of our chief executives http://pewrsr.ch/1O9Phbs