By MICHAEL FALCONE ( @michaelpfalcone )

NOTABLES

• THE FORECAST: President Obama pivots to climate change today, highlighting its dangerous impacts in interviews with local and national meteorologists, including ABC's GINGER ZEE. In the afternoon, the President speaks with meteorologists from New York, San Francisco, Seattle, Chicago, and Columbia, South Carolina. As part of "Weather from the White House," the anchors will spend the day with behind-the-scenes access to the White House and the President's top advisers. ABC's MARY BRUCE notes that the interviews are timed to the release of the third U.S. National Climate Assessment - a report on the impacts of climate change on all regions of the country and key sectors of the economy.

• PRIMARY SEASON REVS UP: 6 KEY RACES IN NORTH CAROLINA, OHIO, AND INDIANA. The primary season is truly upon us as North Carolina, Ohio, and Indiana hold primaries today. Twenty-five states will hold primaries in the next six weeks and today's key one to watch will take us into a fight that will play out all over this country in the coming weeks: the establishment GOP vs. the Tea Party and whether the establishment can finally put down the Tea Party rebellion and re-take the Senate. We'll also watch as a possible 2016 proxy fight between Jeb Bush, Rand Paul, and even Mike Huckabee erupts in North Carolina. The Republican Senate primary in North Carolina is today's key race and pits the establishment against the Tea Party. Thom Tillis, speaker of the North Carolina House, is the establishment candidate backed by Jeb Bush and, just yesterday, Mitt Romney. Here's what else to watch today from ABC's SHUSHANNAH WALSHE: http://abcn.ws/1j6P12t

THE ROUNDTABLE

ABC's JEFF ZELENY: The Republican establishment has been striking back this year, taking a decidedly aggressive posture against Tea Party challengers in races that are key to determining control of the Senate. The biggest test yet comes in a series of May primaries, which will provide early clues to help answer whether the GOP is on track in its quest to win a Senate majority. Today, the fight is underway in North Carolina, with big-name endorsements all around. Will Thom Tillis, the candidate endorsed by Mitt Romney and Jeb Bush win? Or will Greg Brannon, Rand Paul's choice, keep Tillis from winning 40 percent to avoid a run-off race in July? It's a familiar battle, but the GOP establishment hopes the time for ideological purity tests in primaries is over.

ABC's RICK KLEIN: It's the biggest tea party vs. the establishment showdown of the year so far. But the scent of tea has long since permeated the North Carolina Senate race - and will dominate even if the establishment favorite clears 40 percent and avoids a runoff in today's primary. Thom Tillis has an important title (speaker of the North Carolina House) and important people in the GOP backing him (Jeb Bush, Mitt Romney, Newt Gingrich). But is the man who calls himself the "leader of the conservative revolution" in the state capital a raging moderate? The race highlights how establishment names even more than issue areas hold particular resonance; the mere mention of John McCain's support for Tillis drew boos at a campaign event for rival candidate Greg Bannon yesterday, according to the Charlotte Observer. Again, though, the Republican Party's establishment wing has moved in the direction of its tea party brethren. That will hold true regardless of who prevails in North Carolina.

ABC's SHUSHANNAH WALSHE: We are just two weeks away from Kentucky's primary, but a new ad from Senate Minority Leader Mitch McConnell's campaign seems focused directly on the general election, never mentioning his primary opponent Matt Bevin. The positive ad focuses squarely on creating jobs in the Bluegrass State and details where he has saved jobs all over the state calling him a "hero." "Mitch McConnell works for Kentucky jobs," the narrator says. The campaign says it is a "significant six figure buy" and it comes weeks after McConnell was quoted by a local newspaper saying it was "not my job" to boost local economic development. It was quickly seized upon by his Democratic challenger Alison Lundergan Grimes, Kentucky's Secretary of State and has become a campaign issue in the state. This ad aims to shift the conversation and confront the issue head on. Jonathan Hurst, Grimes' senior advisor responded to the ad in a statement saying, "Mitch McConnell has been in Washington for 30 years, yet never proposed a jobs plan for Kentucky. Instead, he has turned Washington into a gridlocked embarrassment, putting himself and his party first." WATCH: http://youtu.be/4rp7TULnXTA

WHAT WE'RE WATCHING

A TALE OF TWO AL FRANKENS: HOW THE COMEDIAN TRANSFORMED INTO AN 'IMPECCABLE' SENATOR. Long before Al Franken took to the political stage as a U.S. senator, he was making the country laugh at politicians' expense as a comedian for "Saturday Night Live." But when this funny guy decided to make a serious run for the Senate six years ago, the jokes more or less stopped. "I'm still funny," the Minnesota Democrat told "The Fine Print's" JEFF ZELENY as he toured rural Minnesota. "I'm funny with my colleagues. My colleagues will all tell you I'm funny." Asked what Franken, the comedian, would say about Franken, the senator, he said dryly that he wouldn't have much material to work with. He chuckled, describing his first term in the Senate as "impeccable." WATCH: http://yhoo.it/1my4iN0

BUZZ

HILLARY CLINTON EXPECTED TO CAMPAIGN FOR CHELSEA'S MOTHER-IN-LAW. It's a family affair for the Clintons, ABC'S BETSY KLEIN and LIZ KREUTZ notes. Just one month after Bill Clinton hit the trail for Chelsea's mother-in-law and grandmother to-be, Marjorie Margolies, Hillary Clinton is expected to join the campaign for a May 15 event, ABC News has learned. This event, first reported by Politico, will mark the first time Hillary Clinton will campaign for a 2014 race. Clinton's lack of involvement in the Margolies campaign had prompted "awkward speculation in Philadelphia that Mrs. Clinton does not want to be burdened by Ms. Margolies's baggage in a state that could be pivotal to her chances in the 2016 presidential campaign, should she decide to run," according to the New York Times. Chelsea Clinton, who is married to Margolies' son Marc Mezvinsky, is prohibited from campaign appearances due to her affiliation with NBC News. Margolies is running to re-take her seat in Pennsylvania's 13th district in a competitive four-way race. http://abcn.ws/1g3HkoJ

BOEHNER TAPS GOWDY TO HEAD BENGHAZI PROBE AS DEMS PONDER NEXT MOVE. House Democrats are sending signals that they may not participate on a new select committee to investigate the Benghazi terrorist attack on Sept. 11, 2012, as House Speaker John Boehner puts the finishing touches on the panel, ABC's JOHN PARKINSON notes. Boehner yesterday tapped Rep. Trey Gowdy, whom he described "as dogged, focused, and serious-minded as they come," to chair the committee, which he hinted will have full subpoena power to call witnesses and obtain documents. "With four of our countrymen killed at the hands of terrorists, the American people want answers, accountability, and justice," Boehner, R-Ohio, stated. "I know [Gowdy] shares my commitment to get to the bottom of this tragedy and will not tolerate any stonewalling from the Obama administration." But the key question remains whether Democrats will even participate in the special investigation. "We haven't seen the language of what they're talking about," House Democratic Whip Steny Hoyer, D-Md., told reporters this afternoon. "We think this is a political not a substantive effort." http://abcn.ws/1fKmi3E

EVA LONGORIA STARTS LATINO POLITICAL GROUP. Former "Desperate Housewives" star Eva Longoria hopes to start a Latino political movement, according to ABC's SERENA MARSHALL. Yesterday, Longoria announced the launch of the Latino Victory Project. She called it a non-partisan effort to create more political engagement among Latinos, even though her co-founder, Henry Muñoz III, is the finance chairman of the Democratic National Committee. Longoria insisted the goal of the group was simply to encourage political participation across the board in the Latino community. "It's important to me that the ballots represent the landscape of America," Longoria said. "It's a very ambitious effort. It's a non-partisan effort. It's never been undertaken before." According to the U.S. Census, Hispanics constitute 17 percent of the nation's total population with approximately 53 million people, accounting for the nation's largest ethnic or racial minority. http://abcn.ws/RlMmXI

OBAMA CELEBRATES CINCO DE MAYO, WARNS GUESTS 'BE CAREFUL' THE MARGARITAS WILL 'SNEAK UP ON YOU.' With the margaritas flowing and the mariachi band playing, President Obama welcomed a boisterous crowd to celebrate Cinco de Mayo at the White House this evening, ABC's MARY BRUCE reports. "Bienvenidos a la Casa Blanca! This is a rowdy crowd, I can tell. They're ready to party," Obama joked. "The margaritas I hear are quite good. Be careful, though, they'll sneak up on you." The president went on to recall the history of Cinco de Mayo and pay tribute to "our shared heritage, our shared history, our shared future" with Mexico. "We can honor our past by building an even brighter future together," he said, citing the Affordable Care Act and his administration's efforts to improve access to education and pass comprehensive immigration reform, which drew huge applause. "Opportunity for all is why I'm fighting so hard to fix a broken immigration system," he said to cheers. "I am convinced that America's prosperity and security depend on comprehensive, common-sense immigration reform." http://abcn.ws/1q8lKJs

BIDEN TOUTS THE UNDOCUMENTED AS 'AMERICANS.' Vice President Joe Biden marked Cinco de Mayo with an impassioned call for immigration overhaul, ABC's ERIN DOOLEY reports. "We don't have to redouble our efforts. We have to redouble our demand. We have to redouble our demand that the House of Representatives takes up legislation that's going to match the strong bill that came out of the United States Senate," the VP said, referring to the upper chamber's Border Security, Economic Opportunity, and Immigration Modernization Act, which passed in the Senate with bipartisan support in June 2013. "It's time for John - he's a good man, John Boehner - to stand up," Biden said of the GOP House speaker. "And other Republicans to stand up. Not for us to stand. We've already stood up. We've stood up, we've been counted. "But it's time for him to stand up, stand up and not let the minority - I think it's a minority - of the Republican party in the House keep us from moving to a vote to change the circumstances for millions and millions of lives." http://abcn.ws/1g2T1vX

SUPREME COURT UPHOLDS PRAYER AT TOWN MEETINGS. The Supreme Court ruled in favor yesterday of a town in New York that begins its public board meetings with a prayer, ABC's ARIANE DE VOGUE reports. In a 5-4 decision, Justice Anthony Kennedy wrote the main opinion saying, "Ceremonial prayer is but a recognition that, since this Nation was founded and until the present day, many Americans deem that their own existence must be understood by precepts far beyond the authority of government, to alter or define and that willing participation in civic affairs can be consistent with a brief acknowledgement of their belief in a higher power, always with due respect for those who adhere to other beliefs." The decision was a loss for two women, Linda Stephens and Susan Galloway, an atheist and a Jew, who filed suit against Greece, N.Y., arguing that they felt coerced to participate in prayers - which are predominately Christian - and delivered by volunteers chosen by town officials. The women won their case at a lower court when a federal appeals court ruled in favor of the women, saying that the town's practice violated the Establishment Clause of the Constitution. http://abcn.ws/1g3kP3q

IN THE NOTE'S INBOX

-BRENT BOZELL ENDORSES JASON CONGER IN OREGON GOP SENATE PRIMARY. The Conservative Victory Committee's Brent Bozell issued the following statement today: "After four years of empty promises from Republican leaders it would be pointless for Oregon Republicans and conservatives to send to Washington another rubber stamp for Mitch McConnell and John Boehner - who together have continuously caved to President Obama on ObamaCare, uncontrollable spending, tax increases and raising the debt that steals from our children. That's why I enthusiastically endorse Jason Conger for U.S. Senate, because he will be a leader who will fight for Oregonians instead of a follower who will kow-tow to the Washington establishment and President Obama."

-ALLIANCE FOR MAIN STREET FAIRNESS UNVEILS NEW AD SERIES. The ads feature a series of traditional small business owners who are being adversely affected by the current tax code. The Senate passed the Marketplace Fairness Act one year ago today; the House hasn't come up with a similar solution yet. WATCH the ads: http://youtu.be/1aSbVbN5OWs and http://youtu.be/hnKPlS0-69c

IN CASE YOU MISSED IT

ALANIS MORISSETTE RECORDS CAMPAIGN THEME SONG FOR CONGRESSIONAL CANDIDATE. If you are a Congressional candidate running in a district that includes celebrity hotspots like Malibu, Beverly Hills and Bel Air, you have to step up your game, ABC'S ALINA KLEINEIDAM notes. And that's exactly what Marianne Williamson did. Williamson, who is running to replace Rep. Henry Waxman, a Democrat who is retiring, in California's 33rd Congressional district, released her official campaign theme song on Monday. It was written and recorded by Grammy award-winning singer and songwriter Alanis Morissette. "I was attempting to capture the passion, mission, activism, deep humanity and tenderness of Marianne, the new political sensibility she represents and the consciousness that produced it," Morissette said in a statement. Williamson said she was "thrilled that Alanis has written and recorded the song," which is titled, "Today." http://abcn.ws/1g3nUAo

WHO'S TWEETING?

@postpolitics: Why Obamacare isn't getting any more popular - and probably won't http://wapo.st/1omuaZ6

?@ajjaffe: More on why outside groups are now paying attention to banker Sid Dinsdale in the #NESen race: http://bit.ly/Q9Ri12

@brianjameswalsh: My thoughts in Bloomberg News on the GOP primary landscape… http://www.bloomberg.com/news/2014-05-05/republican-civil-war-peaks-as-primaries-test-tea-party.html …

@politico: The 1 House race where immigration matters http://politi.co/1jwz992 via @seungminkim

@SalenaZitoTrib: . @GovernorOMalley who has been seriously toying with a run for the Democratic nomination for POTUS hitting the trail in SC for Sheheen.