The Note: Trouble In Mason City, Feat. Hillary Clinton and Rick Santorum

— -- NOTABLES

--YOU REALLY OUGHT TO GIVE IOWA A TRY: Broadway this is not. But if Rick Santorum has anything to do with it, there's going to be trouble today in Mason City, Iowa -- the town famous for inspiring "The Music Man." That's because Santorum, who is expected to declare his presidential intentions later this month, and Hillary Clinton will both converge on the northern Iowa community, holding nearby events a few hours apart. The Santorum team tells The Note they are eager to use the visit to sharpen the contrast with Clinton.

--PICK A LITTLE, TALK A LITTLE: Clinton is scheduled to attend a small grassroots-organizing event. Not counting private fundraisers (i.e. the one Beyonce showed up at) or her unannounced visit to Brooklyn (where Clinton swung by her campaign headquarters and bought a salad and two children's rompers), it's been 13 days since we've seen the Democratic presidential candidate in any official capacity. Even though Clinton hasn't been chattering about herself publicly during this period -- others have been, and now a number of issues and questions have percolated that Clinton will need to address. (Will she take a stance on trade? Why is she not answering questions from the media? Will she address her wealth?)

--YA GOT TROUBLE: Today Santorum will hold town hall meeting at a Pizza Ranch. "There could not be a clearer contrast than that between Senator Santorum and Senator Clinton," a Santorum aide told The Note. "A decade ago, Senator Clinton -- before her many failures as Secretary of State, specifically during the 2009 Iranian Green Revolution -- opposed Senator Santorum's efforts to impose sanctions on Iran's nuclear ambitions. Senator Santorum fought Clinton and won, passing his Iran Freedom and Support Act in 2006. These are among the sanctions that are now bringing Iran to their knees."

--ANALYSIS -- ABC's RICK KLEIN: Jeb Bush wound up spending a week explaining his position on the Iraq war. Is Marco Rubio's turn next? After a few minutes of arguing about the question he was being asked, Rubio on Sunday told Fox's Chris Wallace: "It was not a mistake for the president to go into Iraq based on the information he was provided as president." His distinction may be logically sound; no, he wouldn't have been in favor of the war based on what we now know, but President Bush couldn't have known that at the time, so no, it wasn't a "mistake." But this is a long way from a clean, crisp answer. Rubio is positioning himself as a foreign policy expert, and the facility with which he answers questions on the topic typically impresses. Not this time, though.

IN CASE YOU MISSED IT

JOHN KASICH VIRTUALLY CERTAIN TO RUN FOR PRESIDENT, SOURCES SAY. Ohio Gov. John Kasich is "virtually certain" to jump into the race for the 2016 Republican presidential nomination, sources close to the governor tell ABC News. Kasich has said his wife and daughters have given him a green light to run and in recent days Kasich has told his political advisors to begin preparing for a likely campaign, ABC's JONATHAN KARL reports. If he makes the final decision to run, he will make the announcement in late June or July. This would not be Kasich's first presidential campaign. He ran for the 2000 republican presidential nomination but his campaign quickly fizzled out. At the time he was a Republican congressman from Ohio and chairman of the House Budget Committee. http://abcn.ws/1IFIpWl

THE BUZZ

with ABC's VERONICA STRACQUALURSI

NATIONAL SECURITY TAKES CENTER STAGE AT IOWA GOP DINNER. There was food, drink and plenty of glad-handing, but national security tough-talk stole the show in Iowa. After a week of questions about Jeb Bush and how to view the Iraq war in hindsight, most of the notable Republican candidates and potential candidates took the stage at the Iowa Events Center in Des Moines this weekend, for the Iowa GOP's Lincoln Day Dinner -- the latest early-voting-state event to draw a herd of White House hopefuls. Many of them offered up stern warnings to terrorists and to President Obama for how he's confronted the threat. National security is becoming a staple of GOP candidates' stump speeches at events like this one. ABC's CHRIS GOOD has more. http://abcn.ws/1FlCe72

FIVE STORIES YOU'LL CARE ABOUT IN POLITICS THIS WEEK. Who said a presidential campaign isn't dangerous? You could lose a tooth. Someone could lick your camera. You might accidentally say you're running before you actually are. You could find yourself raising money for the kind of super PAC you say you loathe. Your brother's shadow could envelop your campaign. If you win, kings might still not come over when you invite them. And if you lose, you might wind up in the ring with the former heavyweight champion of the world. ABC's RICK KLEIN highlights the five stories the ABC News political team is tracking in the week ahead. http://abcn.ws/1GgUX4y

BOBBY JINDAL ON IRAQ: 'PARLOR GAMES' AREN'T 'HELPFUL.' Louisiana Gov. Bobby Jindal wouldn't say whether the Iraq war was a good idea in hindsight, but he did say that such hypothetical questions aren't "helpful." Jindal spoke with ABC News after the Iowa GOP's Lincoln Day Dinner in Des Moines, responding to the same question that followed Jeb Bush all week: In hindsight, knowing that intelligence about Saddam Hussein purportedly having weapons of mass destruction was not shown true by history, should the United States have invaded Iraq? "I don't think that the parlor games are helpful," Jindal said when pressed, ABC's CHRIS GOOD reports. "What is helpful," he said, "is that at the time, given the information that they had, President [George W.] Bush made absolutely the right decision. Let's remember, the world is a better place without Saddam Hussein." http://abcn.ws/1GgYboS

RAID ON ISIS LEADER 'PICTURE PERFECT,' SEN. DIANNE FEINSTEIN SAYS. Sen. Dianne Feinstein, the vice chair of the Intelligence Committee, said the "picture perfect" raid that killed an ISIS leader this weekend in Syria is "the kind of one-two punch that we should do more of" to combat ISIS. "I believe that if we're not going to put troops on the ground, then we've got to use our Special Operations Forces to go in and collect intelligence; also be able to capture people that might be able to be helpful," she said Sunday on "This Week." According to U.S. officials, the Army's elite Delta Force unit killed Tunisian Abu Sayyaf, a senior ISIS leader involved in the group's illicit oil and gas trade, in an attempt to capture and interrogate Sayyaf about hostages and the terror group's finances. On the continuing strength of ISIS, Feinstein called the group "organized" and "an impressive fighting force," according to ABC's STEPHANIE EBBS and BEN SIEGEL. http://abcn.ws/1JRnhtc

SENATE MAJORITY LEADER MITCH MCCONNELL ON NSA PROGRAM: 'VERY IMPORTANT' TO COMBAT TERROR THREATS. Senate Majority Leader Mitch McConnell underscored his support Sunday for the controversial NSA program for bulk collection of domestic phone records. "This has been a very important part of our effort to defend the homeland since 9/11," McConnell said Sunday on 'This Week.' The PATRIOT Act, which provides the authority for the NSA collection program, is set to expire at the end of the month, but McConnell said he favors a short-term extension of the program. That stance puts him at odds with the presidential candidate he's supporting in 2016 -- Sen. Rand Paul, whom the leader praised for embracing a "new brand of Republicanism." Paul has threatened to filibuster the reauthorization of the NSA program that McConnell supports, ABC's ARLETTE SAENZ reports. http://abcn.ws/1cIyBgh

SOCIAL SQUARE

BEN CARSON LED RAND PAUL, TED CRUZ IN FACEBOOK INTERACTIONS THIS MONTH. The number of Facebook interactions related to Republican presidential candidate Ben Carson were more than double those related to Sen. Rand Paul, who he is competing against for the GOP nomination for president in 2016. Facebook, which provided the approximated data to ABC News, defines interactions as posts, comments, likes and shares. The social network measured the interactions between May 6 and May 12 of this year. Carson formally declared a run for the White House just days before the measured time period. The Kentucky senator garnered about 1 million interactions, while Carson, the pediatric neurosurgeon, achieved about 2.2 million, ABC's BENJAMIN BELL notes. http://abcn.ws/1e9qCtX

WHO'S TWEETING?

@CahnEmily: This @nytimes graphic on the presidential candidates' staff networks is awesome http://nyti.ms/1PQFtF5

@nationaljournal: Mike Huckabee hasn't changed, but the primary calendar has. Now he aims to exploit it http://buff.ly/1ESqIvy

@ZekeJMiller: In foreign policy speech today, @GovChristie will call fears over NSA spying "baloney" http://time.com/3882102/chris-christie-foreign-policy-military/

@margarettalev: Hillary Clinton pivots from big money to small business (by @Jeneps) http://bloom.bg/1FjmkZJ via @bpolitics @jeneps

@jimrutenberg: Campaigns move more functions out of regulatory regime meant 2 curb donor influence @nickconfessore @EricLichtblau http://www.nytimes.com/2015/05/18/us/politics/super-pacs-are-remaking-16-campaigns-official-or-not.html?smid=nytnow-share&smprod=nytnow