 -- NOTABLES

--WHY BERNIE SANDERS’ WEST COAST BLOWOUTS MATTER: Bernie Sanders did not just win all three states that voted this weekend -- Washington, Alaska and Hawaii -- he won them by overwhelming, impressive margins, ABC’s MARYALICE PARKS notes. The presidential hopeful won every county in Washington, and some of his biggest victory margins came from the state's most rural and traditionally conservative areas. The win will likely mean a fundraising boost for the small-donor driven campaign. Sanders does not have a super PAC and instead has enjoyed injections of cash from his fans after big wins or important nights in the election calendar. http://abcn.ws/1ML7w8d

--THE WINS ALSO VALIDATE SANDERS' COMMITMENT TO AN EXTENDED PRIMARY: Despite the fact that he is trailing Hillary Clinton by a significant number of delegates needed for the nomination, Sanders has pledged to stay in the race until all 50 states get their say. Since all delegates on the Democratic side are awarded proportionally, Sanders will receive a sizeable number of delegates from Saturday’s blowouts and dent Clinton’s delegate lead. http://abcn.ws/1ML7w8d

--ANALYSIS -- ABC’s RICK KLEIN: At what point will margins matter? The fact that Bernie Sanders is racking up enormous wins (three weekend blowouts, after taking two of three contests last Tuesday) is starting to shake up a critical Clinton camp narrative: that March is the month she effectively locked the nomination away. Clinton remains in control in the delegate math, with or without the supers. But a candidate who has already won just shouldn’t be losing by 40-odd points in three different states on the same day. The latest wins will help (along with the online donors they will intrigue) fuel Sanders through Wisconsin, Pennsylvania, New York, and California beyond – keeping Sanders’ message on the air and the pressure on Clinton intense as ever. It may even be enough to lock in the debates neither camp seemed to want anymore after the last exchange, in Miami. Clinton would rather be talking about Donald Trump, and, Monday at least, Chuck Grassley and Senate Republicans. But there’s a whole lot of Democratic primary voters who seem to really, really want their say first.

HAPPENING TODAY -- CLINTON TO GIVE SPEECH ON SUPREME COURT VACANCIES. Today, Hillary Clinton will weigh in on the Supreme Court vacancy left by Antonin Scalia. In her scheduled speech at the University of Wisconsin-Madison, Clinton will argue that the vacancy underscores the high stakes in this election and urge Americans to keep this in mind as they cast their vote. The Democratic hopeful plans on stating that Senate Republicans must be prevented from succeeding in their strategy of refusing to consider the President’s nominee. Clinton will specifically call on Sen. Chuck Grassley, who is Chairman of the Judiciary Committee, to commit to giving President Obama’s nominee Judge Merrick Garland a hearing. Clinton will also focus on Republican frontrunner Donald Trump and try to make the case that voters should be concerned about who President Trump would nominate.

LAST WEEKEND ON THE TRAIL with ABC’s VERONICA STRACQUALURSI

TRUMP, CRUZ TRADE BARBS OVER NATIONAL ENQUIRER REPORT. Donald Trump blamed rival Ted Cruz for starting a spat leading up to a report in the National Enquirer claiming "political operatives" are looking into rumors that the Texas senator had multiple marital infidelities.. "I had nothing to do with it. The campaign had absolutely nothing to do with it," Trump told ABC's Jonathan Karl on "This Week" Sunday. "I have over control over the National Enquirer." Trump said it was "disgraceful" that Cruz had blamed him for the story. “For him to try and say that I had to do with it, to put the shoe on the other foot, is disgraceful,” Trump said, adding, “By the way, he’s the one that started it,” referring to an ad by an anti-Trump super PAC that featured a racy image of Trump's wife Melania from her days as a model. Trump also declined to say whether he condemned the National Enquirer report or whether he thought it was accurate. "I don’t care. The National Enquirer did a story. It was their story -- it wasn’t my story," he said. ABC’s NICKI ROSSOLL and JESSICA HOPPER has more. http://abcn.ws/1Rx6FMs

WILL PRESIDENT TRUMP GO ON TWITTER TIRADES IF ELECTED PRESIDENT? Donald Trump has made a habit of taking his fights with other candidates from the campaign trail to the Twittersphere, recently drawing criticism for retweeting a photo of Ted Cruz's wife, Heidi, and his wife side-by-side with the caption, "The images are worth a thousand words." And if elected president, Trump may use 140 characters to take on world leaders. "Would you be doing late night Twitter wars with world leaders who insulted you?" ABC's JONATHAN KARL asked Trump on "This Week" Sunday. "It's a new way of communicating. It's very effective. I've been very effective with it," Trump replied. Trump suggested other people may not like Twitter, or other social media platforms, because they do not have many followers. "It's a great way of communicating, as far as I'm concerned, but I'm not going to be doing it very much as president," Trump said. "I will act in the best interests of our country. I will act to protect our country, whether that's counter-punching or not." http://abcn.ws/1Rnp6Es

TRUMP: ‘I DON’T THINK AMERICA IS A SAFE PLACE FOR AMERICANS.’ Donald Trump says he doesn't believe American citizens are safe in their own country. The frontrunner for the GOP's nomination expressed his concerns after he was asked whether Americans should feel safe traveling to Europe following last week's terror attacks in Brussels. Bombings at the capital's airport and a metro station killed 28 people, including at least two Americans. "I don’t think America is a safe place for Americans, you want to know the truth,” Trump said, later adding, "We're allowing thousands of people to come in here. Nobody knows where they're from. Nobody knows who they are and they're coming in here by the thousands and let me tell you something, we're going to have problems." While it was unclear which groups Trump was referring to, he proposed banning all Muslims from entering the U.S. following the Nov. 13 attacks in Paris and wants to build a safe zone for Syrian refugees instead of allowing them to enter the U.S, ABC’s BEN CANDEA and NICKI ROSSOLL report. http://abcn.ws/25qXS5X

WHO’S TWEETING?

@TheFix: Let's uproot the pernicious, unproven claim that Ted Cruz attacked Donald Trump's wife http://wpo.st/T6qP1

@TomBeaumont: OSHKOSH, Wisconsin (AP) -- A solid Cruz win in Apr 5 WI primary would narrow Trump's path, raise convention worries. http://bigstory.ap.org/urn:publicid:ap.org:3f01a5f79eab4fe6856a9efcac2e86b8 …

@bterris: Now with new baby, Ivanka Trump, the ‘Anti-Donald’, works to protect the billion-dollar brand, via @marycjordan http://wapo.st/1SpF2oG

@chrisgeidner: North Carolina Sued Over Anti-LGBT Law. Read the lawsuit, filed in fed ct overnight, at @BuzzFeedNews: http://www.buzzfeed.com/dominicholden/nc-anti-lgbt-law-lawsuit?utm_term=.dx7LB2b4P …

@AaronBlake: Are Donald Trump voters responsible for surging GOP turnout? Probably not. http://wpo.st/_0qP1