The Note: Scott Walker and the Death of a Presidential Candidacy

— -- NOTABLES

--SCOTT WALKER DROPS OUT, WANTS TO TAKE TRUMP DOWN TOO: After a dramatic fall from the top tier of the Republican presidential candidates over the last several weeks, Wisconsin Gov. Scott Walker ended his bid for the White House yesterday, ABC's RYAN STRUYK and JORDYN PHELPS report. "Today, I believe that I'm being called to lead by helping to clear the field in this race so that a positive conservative message can rise to the top of the field. With this in mind, I will suspend my campaign immediately." Walker announced at a press conference in Madison, Wisconsin. "I encourage other Republican presidential candidates to consider doing the same, so that the voters can focus on a limited number of candidates who can offer a positive, conservative alternative to the current front runner," Walker went on to say, referring to Donald Trump. http://abcn.ws/1YwmneH

--BACKSTORY: In recent weeks, Walker has fallen dramatically in national polls, registering at less than 0.5 percent in the latest national CNN/ORC poll this weekend. In Iowa, where for much of the year Walker was considered the favorite to win the first in the nation caucuses, Walker slid from 19 percent to 5 percent in just six weeks of NBC News/Marist polling. Walker first gained attention in Iowa for a speech at the Iowa Freedom Summit in January. But after riding high in the polls in that state for over half the year, Walker was outpaced in the polls following a lackluster performance in the first televised Republican debate. http://abcn.ws/1YwmneH

--ANALYSIS -- ABC's RICK KLEIN: Scott Walker's exit is a jolt to a chaotic and still churning presidential race. It also challenges some of the biggest assumptions that have governed understanding and analysis of the 2016 cycle. First, early polls really, really don't matter. The candidate with the best six months of 2015 is gone one quarter later, without a scandal or an "oops" to blame for it. Second, super PACs are overrated. Yes, they can provide critical air cover, but only if you have a real operation on the ground. Giant outside entities could save neither Walker nor Rick Perry, who struggled with hard dollars despite being established, big-state governors with national fundraising bases. Finally -- and most significantly -- this most crowded primary in recent history could get quite a bit roomier. If the dollars don't exist to support 17 candidates, they most likely can't sustain 15 serious candidacies either. Walker wasn't a candidate long enough to even file an FEC report; those reports will be scrutinized for burn rates in a few weeks, with the possibility of some flameouts even before then.

POPE WEEK IN THE NOTE. Pope Francis arrives in Washington, DC later today for his week-long visit to the United States and The Note will be setting aside a special place for daily insight and analysis of the Holy Father's trip. As our guide, we've enlisted the help of Father Michael A. Russo, former professor of Communication Studies at Saint Mary's College of California, an expert on the papacy who is serving this week as a media consultant for the U.S. Conference of Catholic Bishops. In today's installment, we asked Father Russo (@frmikerusso), who also blogs at http://francisfactor.com/, two questions: Why do popes travel and what's the overall goal for these visits?

--FR. RUSSO: "This pope, like his predecessors, walks in the footsteps of the apostles, casting his presence and special grace on people. Several weeks ago, we saw a glimmer of this presence when Pope Francis appeared in a 'virtual audience' on ABC News with David Muir as moderator. The pope appeared to be deeply and emotionally connected to the participants in Chicago, Los Angeles and McAllen, Texas. He asked a student from Chicago's Cristo Rey High School to sing for him, and added encouragement, 'Go on, you can do it. Be courageous!' Later in the broadcast, Pope Francis called out to a religious sister who works with recently-arrived immigrants in her border town of McAllen, Texas, and he thanked all religious women for their good works, saying, 'I love you all very much.'

"His simple words of encouragement, in pitch perfect gratitude, speak to people directly and with sincerity. Such examples of "strategic communication" -- the kind of persuasive language that is so hard to come by -- is a unique gift possessed by very few leaders, and comes "person to person," and only in limited supply. At certain moments, almost mysteriously, a Pope John XXIII, a Martin Luther King, a Mother Teresa of Calcutta, a Nelson Mandela have caught the world's spiritual imagination and have possessed the moral authority to truly challenge the minds and hearts of millions. This visit of Pope Francis to our country places him among these extraordinary spiritual leaders."

TODAY ON THE TRAIL with ABC's SHUSHANNAH WALSHE: Hillary Clinton and Jeb Bush are both in Iowa. Clinton, at an event in Des Moines, is expected to present her plan to bring prescription drug prices down. Bush holds events in Cedar Falls, Gladbrook and Cedar Rapids. Rick Santorum is also in Iowa, attending a candidate forum luncheon in Des Moines. Ben Carson holds three events in the critical state of Ohio, as well as a press conference. Both Carly Fiorina and Mike Huckabee are in South Carolina. Fiorina will attend a national security forum in Charleston, as well as hold a town hall in Myrtle Beach. Huckabee officially files for the presidential primary in Columbia and holds two other events in the state in the late afternoon. Lindsey Graham is in Manchester, New Hampshire attending a dinner for the Financial Management Association. Bernie Sanders plans on attending and speaking at a strike this morning on Capitol Hill with federal contract workers who provide food and cleaning services in the Capitol. They are calling for a $15 minimum wage ahead of the Pope's visit. They are also planning a prayer action" during the protest.

THE BUZZ

with ABC's PAOLA CHAVEZ and VERONICA STRACQUALURSI

HOW SCOTT WALKER'S PRESIDENTIAL CANDIDACY CRUMBLED. Scott Walker is now officially out. Amounting to one of the shortest presidential campaigns in modern history -- lasting just 71 days -- Walker had seen his polling numbers crater in recent months compared to the time ahead of his entry into the field, when he was widely viewed as one of the most promising contenders. Running as a Washington outsider and heralded for his success in pushing through conservative reforms in the politically purple state of Wisconsin, Walker's campaign began to lose steam almost as soon as it was launched. So what happened? ABC's JORDYN PHELPS reports: http://abcn.ws/1itOcn0

--THE MONEY: The size and scope of Walker's campaign, which was reportedly comprised of some 90 paid staff, had been built for a frontrunner. And when Walker failed to perform as such, the fundraising simply couldn't keep up with the operation. Reed Galen, a Republican political consultant who served as John McCain deputy campaign manager until July 2007, points out that the campaign never had the benefit of frontrunner status while Walker was actually in the race, since Walker's strongest stretch in the polls -- particularly in Iowa -- came before he was a declared candidate. "The campaign did not exist with the benefit of being a frontrunner," Galen said. http://abcn.ws/1itOcn0

--THE MESSAGE: Stanley Hubbard, a Minnesota media mogul who had previously been one of Walker's top donors, told ABC News in an interview prior to the news that he was dropping out of the race, that he was planning to withdraw his exclusive support from Walker and give money to a number of other Republican candidates, including Chris Christie, Carly Fiorina, and Ben Carson. Hubbard also recommended media coaching to the governor as a means to improve the power of his messaging. "Why does one person come across and someone else doesn't?" Hubbard said. "I've been in TV business a long time and there are ways you can get training to get your message across....And if Scott can't figure that out, he might as well drop out," Hubbard added. And drop out he did. http://abcn.ws/1itOcn0

CARLY FIORINA SAYS BEN CARSON 'WRONG' ON MUSLIM PRESIDENT COMMENTS. Responding for the first time to Ben Carson's comment that he would not advocate for a Muslim president in an interview on NBC's "The Tonight Show," Republican presidential contender Carly Fiorina said Carson's position is "wrong," ABC's JORDYN PHELPS notes. "I think that's wrong," Fiorina told Jimmy Fallon in an interview on Monday. "You know, it says in our Constitution that religion cannot be a test for office. It is also true that this country was founded on the principle that we judge each individual and that anyone, of any faith, is welcome here." http://abcn.ws/1OrVl4O

CARSON DOUBLED DOWN ON HIS OPPOSITION to the concept of a Muslim presidential candidate, taking to Facebook on Monday to answer a couple questions as part of his "Ask Ben" series that the campaign does a few times a week. "Know this, I meant exactly what I said," Carson wrote in the Facebook post. "I could never support a candidate for President of the United States that was Muslim and had not renounced the central tenant of Islam: Sharia Law." Carson reiterated that he could not support a Muslim candidate for president "until these tenets are fully renounced." http://abcn.ws/1OrVl4O

MUSLIM GROUP SLAMS BEN CARSON AS 'UNFIT TO LEAD.' A prominent U.S. Islamic group Monday called for Ben Carson to withdraw from the 2016 presidential race after his weekend comment that he would not support a Muslim for president, ABC'S KATHERINE FAULDERS reports. "Mr. Ben Carson is wrong today to assume and say that American Muslims should not be president of the U.S.," Nihad Awad, national executive director of the Council on American-Islamic Relations (CAIR) said at a news conference Monday. CAIR leaders, visibly outraged, said they invite Carson to meet with them. http://abcn.ws/1KuHx3t

IN CASE YOU MISSED IT

SUPREME COURT JUSTICE RUTH BADER GINSBURG DITCHES HER GAVEL TO PLAY DJ. Supreme Court Justice Ruth Bader Ginsburg made her DJ debut on Monday, ABC'S PAOLA CHAVEZ notes. "DJ RBG" joined Lisa Flynn, a host at the Chicago classical radio station WFMT, in the broadcast booth and shared some of her favorite tunes with listeners. http://abcn.ws/1KHKReY

WHO'S TWEETING?

@MarkHalperin: Gang of 500 CW now: Walker out benefits Rubio most; voter resistance to Jeb is intense; Christie 2nd chance coming; Hillary can be beat

@JamesPindell: Walker might be thinking this is his 2006 dropout before the comeback but the way he blindsided major donors Monday may prevent that.

@ConsultReid: Tea Party Express just called on Alan Grayson to drop out of FL SEN race. Which is pretty much exactly the opposite of what the NRSC wants.

@mattcanter: Whether R's want to hear it or not, this is what the Pope wants: Senate Ds Unveil Aggressive Climate Change Bill http://nyti.ms/1MGdfQP

@nationaljournal: How the God Lobby is preparing for Pope Francis's visit http://njour.nl/s/73280