The Note: Trump Takes To the Airwaves

— -- NOTABLES

--ANALYSIS -- ABC’s RICK KLEIN: It’s Big Dog season, and who better (who else, really?) to welcome Bill Clinton to the campaign trail than Donald Trump? The challenge for Clinton will be to be helpful without being harmful – and that means being approximately as non-controversial, even boring, as he’s capable of being in the run-up to Iowa and New Hampshire. Enter Trump into this equation, with his mocking Tweets and outright threats to make the former president’s sexual indiscretions into fair campaign game. Barack Obama’s rise got under Clinton’s skin in ways that weren’t helpful back in 2007-2008. This time it’s Trump who is most likely to get Clinton off message; unlike Obama, he’s actually trying to do just that. Clinton may be more disciplined than he was eight years ago. But rope lines near Bill Clinton will be the most interesting place in politics for the next few weeks.

--TODAY ON THE TRAIL with ABC’s RYAN STRUYK: We’re exactly four weeks away from the Iowa caucuses – and the 2016 presidential race is switching into high gear. Republican frontrunner Donald Trump is holding a rally in Massachusetts tonight after releasing his first television ad of his 2016 campaign and bashing his main Democratic rival Hillary Clinton over former President Bill Clinton’s sex scandal. Trump’s main rival in the crucial first-in-the-nation caucus state of Iowa, Ted Cruz, is hosting a whopping five events in Iowa today during his bus tour – running all the way until 11:45 p.m. Chris Christie, hoping to sustain his momentum in New Hampshire, will hold three events today, including a speech on leadership. Marco Rubio, who plans to make a national security speech this morning, will be in both Iowa and New Hampshire today. John Kasich will also be in both early states. Rand Paul and Carly Fiorina will join him in New Hampshire. And Mike Huckabee is also in Iowa today.  On the Democratic side, Hillary Clinton spends her day in Iowa, hosting two town halls this afternoon and an event tonight. Former President Bill Clinton, under fire from Trump over his past scandals, is also on the campaign trail today. He’ll hold an event this morning and a town hall late this afternoon in New Hampshire. And he’ll have company there: Clinton’s main rival Bernie Sanders holds two events in New Hampshire, where Sanders has the best chance of toppling her in an early state.

IN THE NOTE’S INBOX

--AMERICA RISING RELEASES NEW VIDEO BRACKETING BILL CLINTON. Just in from the GOP opposition research group, America Rising PAC: A new video that questions whether Bill Clinton’s return to the campaign trail on behalf of Hillary Clinton is an asset or liability. From the group’s communications director, Jeff Bechdel: “If his gaffe-filled 2015 is any indicator, Bill Clinton has a lost a few miles an hour off his fastball. In 2016, he's less a ‘secret weapon’ on the campaign trail and closer to a walking liability. From his astonishingly tone deaf comment about ‘paying the bills’ to the convergence of money and politics at the Clinton Foundation, Bill Clinton reinforces all the negative attributes voters assign to Secretary Clinton: unethical, dishonest and untrustworthy.” According to the group, the video will be backed by a strong social media campaign from America Rising PAC with specific targeting on Facebook, Twitter, and via e-mail. WATCH: https://youtu.be/BSRoqEjXGeU

--BUSH’S NEW AD IN NEW HAMPSHIRE. Ahead of Jeb Bush’s three day swing to New Hampshire this week, the Bush campaign unveiled a new TV ad running in New Hampshire. The ad, titled “Force," focuses on Bush's call for the U.S. to lead a coalition “to take out ISIS with overwhelming force” made in a speech at The Citadel. WATCH: https://youtu.be/-elGMD1a0tQ

YESTERDAY ON THE TRAIL

HILLARY CLINTON SHUTS DOWN HECKLER: 'YOU ARE VERY RUDE'. Hillary Clinton on Sunday confronted a female heckler who interrupted the Democratic candidate's first campaign event of the new year in an attempt to ask about Bill Clinton's conduct towards women, ABC’s LIZ KREUTZ notes. "You are very rude and I'm not going to ever call on you," Clinton told the woman, who later identified herself as Republican New Hampshire State Rep. Katherine Prudhomme O'Brien. Clinton's response drew applause and a standing ovation from many in the crowd of roughly 750 who were packed into an auditorium of a Derry, New Hampshire, middle school. During the Q&A portion of the town hall, O'Brien, who represents Derry, the town where Clinton’s event was held, repeatedly stood up and yelled out to Clinton. What she was saying was inaudible to reporters sitting in the back of the room, and it’s unclear if Clinton was able to make out what she was saying. http://abcn.ws/1ODkdBJ

NOTED: CLINTON PRAISES OBAMA. Clinton, who has made gun control a focal point of her campaign, was quick to offer her support of President Obama’s gun control plan, meanwhile warning that Republicans would take a reverse course. “I'm very hopeful and excited that the President is going to take some action with executive orders in the next week or two to try to get more gun sellers to conduct background checks,” she said at a town hall yesterday in Concord, NH. "I know that a Republican president would delight in the very first day, reversing executive orders that President Obama has made, including this one that we expect him to make.” Clinton has also said she would take executive action on gun control should she become president.

BEN CARSON RESPONDS TO STAFF SHAKEUP. Republican presidential candidate Ben Carson says the decision to shake up his campaign staff came after a “deep dive” into his operation, which showed the campaign’s inability to execute a plan, ABC’s KATHERINE FAULDERS notes. "We have had very good people that had very good ideas and no one predicted that we would even be in the hunt,” Carson said Sunday on ABC's "This Week." "It really is quite spectacular what we were able to do. But the fact of the matter is now we’re in a different ballgame and we need the ability to execute and not just have good ideas." The comments came after three of his top aides -- including campaign manager Barry Bennett and communications director Doug Watts -- announced Thursday they were resigning from the campaign. Deputy campaign manager and policy director Lisa Coen has also resigned, according to Carson's new campaign manager, Ed Brookover. http://abcn.ws/1TxINrL

BERNIE SANDERS SLAMS DONALD TRUMP FOR ATTACKS ON CLINTONS. Democratic presidential candidate Bernie Sanders slammed Republican front-runner Donald Trump for his attacks on Bill Clinton and what he deemed his false campaign rhetoric, suggesting Trump turn his attention to real issues facing the American people, like climate change and the minimum wage, ABC’s ALANA ABRAMSON notes. “We have more things to worry about than Bill Clinton’s sexual life,” Sanders said Sunday on ABC’s “This Week.” Sanders also stood by his previous statement that Trump is a "pathological liar." “I do not get engaged in personal attacks but Trump is over the edge,” he said. "The guy just comes up with things off the top of his head that are lies and someone has to say that.” http://abcn.ws/1VyPlb6

WHO’S TWEETING?

@bgittleson: Santorum out w/ his first TV ad this week, to air in Iowa. Hits Cruz, showing him reading "Green Eggs and Ham" https://vimeo.com/150546514 

@ByronYork: Henry Barbour: 'I have come to believe that the core group of people who are for Trump, you cannot pull them off with a crowbar.'

@SabrinaSiddiqui: Rubio gets question from Miss America Outstanding Teen in NH, quips he wouldn't say the wrong name when giving out the prize.

@TeddyDavisCNN: per Wash Post: Trump camp declined to name person responsible for producing ads- but said he has good track record

@amyewalter: When a guy who wants to ban Muslims and build a wall is in 1st place, hard to see why Christie’s puffery on terrorism hurts him in primary