The Note: A Clash Over Trump

— -- NOTABLES

--THOUSANDS RALLY FOR TRUMP, PROTESTERS CLASH OVER IMMIGRATION POLICY: A nasty protest broke out last night over immigration after the Donald Trump rally in Dallas, Texas, ABC's JOHN SANTUCCI reports. Anti-Trump protesters chanted "Dump the Trump" as police mounted on horses sought to defuse the situation. Officials said there were no arrests and the event concluded without incident.

--HILLARY CLINTON DOES HER BEST TRUMP IMPRESSION: During a campaign stop at Luther College in Decorah, Iowa yesterday, the Democratic presidential candidate mocked Trump's "Make America Great Again" stump speech by doing her best impression of the billionaire Republican presidential front-runner. In front of a crowd of college students, Clinton first went after the seriousness of Trump's candidacy, ABC's ALEC GOODWIN notes. "I have to admit, Donald Trump is entertaining," she conceded. Clinton then launched into a brutal imitation of Trump's campaign rhetoric. "Oh, listen, I don't need to tell you anything. When I get there, peace will be breaking out everywhere, prosperity will be raining down upon you, we will have the new age," she said, pretending to be the Donald. http://abcn.ws/1irE1zN

--ANALYSIS -- ABC's RICK KLEIN: If the first debate was all about Donald Trump, the second debate figures to be about the anti-Trump. The Republican race has not so much changed as it has solidified over the past six weeks, erasing any doubt about Trump's front-running status. But now, Trump will have a different on-stage neighbor - Dr. Ben Carson - and a whole stage full of rivals who need to move to Plan B when it comes to handling the man in the middle. Trump is about to see more incoming fire than even he (maybe) is capable of effectively returning. The Club for Growth is announcing its anti-Trump media campaign on Tuesday, and Wednesday night is primed to become a Trump pile-on. It brings a new set of dynamics to the race - or, at least, the hope of that when it comes to the 15 candidates not named Trump.

--BERNIE SANDERS GETS RESPECTFUL WELCOME AT CONSERVATIVE CHRISTIAN COLLEGE: Liberty University, the conservative, religious college that has been a mainstay for Republican presidential hopefuls for decades, got its first visit of the 2016 election cycle from a Democratic presidential candidate on Monday, ABC's MARYALICE PARKS reports. A Christian rock band welcomed Vermont's independent, fiercely liberal Sen. Bernie Sanders, who is the first Democratic candidate to accept the university's standing invitation to all presidential contenders to address its student body. At Liberty, the college where Sen. Ted Cruz (R-Texas) announced his candidacy, Sanders did not placate or sidestep his on stance on social issues like gay marriage or abortion, but instead began his speech by asking the crowd to look past them. "We disagree on those issues. I get that," he said. "But let me respectfully suggest that there are other issues out there that are of enormous consequence to our country and the world and that maybe, just maybe, we don't disagree on them." http://abcn.ws/1FJ9iD7

TODAY ON THE TRAIL with ABC's RYAN STRUYK

It's a very quiet day on the trail as the Republican field makes their final preparations for the second debate tomorrow night. Republican frontrunner Donald Trump has an event tonight at 8:30 p.m. in Los Angeles aboard the U.S.S. Iowa. Democratic frontrunner Hillary Clinton is off the trail after two events in Iowa yesterday, but her daughter Chelsea is in New York City tonight for a book tour. The conservative group Club for Growth is expected to release a campaign ad this morning in DC. The rest of the Republican and Democratic fields are off the trail.

THE BUZZ with ABC's PAOLA CHAVEZ

HILLARY CLINTON RESPONDS TO ABC/WASHINGTON POST POLL. A reporter asked Clinton about our new ABC News/Washington Post poll that showed a huge drop in her support among women at today's press availability, ABC's LIZ KREUTZ reports. "You know, I'm not one of those who ever thought this was going to be a straight shot," Clinton said. "I've been and around enough campaigns to know there's an ebb and flow -- polls go up and down, people's attention and decision making changes over time. I feel very confident about where we are in the campaign and very committed to doing everything I can to make my case as effectively as possible to women and men and I think that will be successful."

HILLARY ON BILL FOR VP: "IT'S CROSSED MY MIND." Hillary Clinton, who we know is trying to show more of her fun side, sat down for an interview with Mario Lopez of Extra that aired last night, notes ABC's LIZ KREUTZ. Clinton talks about meeting Kim Kardashian, gives advice for Kanye West on running for president, and says she's watching Trump with "some concern" because of his "inflammatory and destructive" comments. She also admits she has contemplated choosing Bill Clinton as her running mate. "He would be good, but he's not eligible, under the Constitution he has served his two terms and I think the argument would be as Vice President it would not be possible for him to ever succeed to the position, at least that's what I've been told...it has crossed my mind," she said.

4 THINGS THAT TOOK SCOTT WALKER FROM FRONTRUNNER TO LONGSHOT CANDIDATE. When Scott Walker entered the 2016 presidential contest, he was considered one of the most promising Republican contenders for the White House. A governor with a record of conservative reforms in the purple state of Wisconsin, Walker launched to the top of the polls in Iowa following a fiery speech at January's Iowa Freedom Summit and stayed there for the better part of the year. So when he officially entered the race in July, Walker seemed like a near shoo-in to win the first in the nation caucuses in the neighboring state. Just two months after launching his campaign, ABC's JORDYN PHELPS reports the polls tell a very different story. http://abcn.ws/1Oqe2og

WALKER MAKES POINTED ATTACK AGAINST TRUMP: "THIS IS NOT OUR PARTY." In an interview on FOX News yesterday, Scott Walker offered up his most direct and pointed attack against Donald Trump, telling Megyn Kelly that "people are sick of tired of" Trump's personal attacks and that his behavior is not befitting of the Republican Party. "I think people are sick and tired of it," Walker said, coming specifically to the defense of Carly Fiorina following Trump's remarks about her face. "I think the more people listen to it the more they realize this is not our party, this is not the country - certainly not the country that I grew up in," Walker continued. "People have different opinions, but you don't have to trash talk people to do it." Making the case that he is the most tested candidate in the field, Walker said he believes voters will come back from Donald Trump to the proven solutions he offers because "they want someone who is for something, not just against something and not just about personal attacks." On the topic of Wednesday night's upcoming debate, Walker told Kelly he is going to be more aggressive and passionate on the debate stage than he was last time around, according to ABC's JORDYN PHELPS.

TWITTER UNVEILS NEW FEATURE: DONATE TO A CAMPAIGN WITH A TWEET. Starting today, you can now donate to campaigns by simply Tweeting. Twitter announced they have teamed up with Square to allow anyone in the U.S. to make a donation directly to a US candidate within 140 characters. From the press release: "This is the fastest, easiest way to make an online donation, and the most effective way for campaigns to execute tailored digital fundraising, in real time, on the platform where Americans are already talking about the 2016 election and the issues they are passionate about."

IMPROVING TREND FOR OBAMA ON THE ECONOMY. Numerically more Americans approve than disapprove of the way Barack Obama is handling the nation's economy, only the fifth time that's occurred in ABC News/Washington Post polls since the second year of his presidency. ABC's GARY LANGER reports, while the 49-47 percent division on his economic performance is within the poll's margin of error, it's a rare result: Obama's been numerically in the black on this measure in just five out of 53 ABC/Post polls since 2010: that June, twice after his re-election in 2012, last March and now. http://abcn.ws/1KOyXSl

WHAT YOU SHOULD KNOW ABOUT THE WHITE HOUSE COLLEGE SCORECARD. The White House is hoping to take a bite out of America's ever-growing student debt crisis with a new way to inform prospective students about college costs and job prospects, says ABC's SUSANNA KIM. The College Scorecard provides data about nearly every post-secondary institution in the U.S., including two-year and four-year colleges and universities. Students can search for the average cost, graduation rate, salary after attending and more. In his weekly address on Saturday, President Obama introduced the scorecard and said, "Right now, however, many existing college rankings reward schools for spending more money and rejecting more students at a time when America needs our colleges to focus on affordability and supporting all students who enroll." http://abcn.ws/1ObfmfJ

POLLING NOTE: EQUAL TREATMENT PREVAILS IN VIEWS ON GAY MARRIAGE: Most Americans say equality under the law trumps individual religious beliefs, according to ABC's GREGORY HOLYK. This view leads to broad support for requiring recalcitrant County Clerk Kim Davis to issue marriage licenses to gay and lesbian couples. In general, 74 percent in this ABC News/Washington Post poll say that when a conflict arises, the need to treat everyone equally under the law is more important than someone's religious beliefs. In the specific case at hand, 63 percent say Davis, of Rowan County, Kentucky, should be required to issue marriage licenses despite her religious objections. Davis was jailed briefly by a federal judge for refusing to obey his order to issue marriage license to gays and lesbians, as required by the Supreme Court's decision on this matter in June. She was released after others in her office began issuing the licenses. Among those who say Davis should be required to issue the licenses, 72 percent also favor the decision by U.S. District Judge David Bunning to jail her. http://abcn.ws/1NshNc3

WHO'S TWEETING?

@ABCLiz: 20-year-old sophomore asked Clinton to name policy differences w Sanders. "l think there will be plenty of time for us to debate," she says

@realdonaldtrump: To all my fans, sorry I couldn't do The Apprentice any longer-but equal time (presidential run) prohibits me from doing so. Love!

@1PatriciaMurphy: Hillary Clinton losing the voters she needs most- Democratic women: thedailybeast.com/articles/2015/...

@thehill: Dr. Phil: People are "living vicariously" through Trump http://hill.cm/SkUa2dA

@politico: Watch the GOP contenders try to out-Reagan one another http://politi.co/1URtJEX | Getty