Sadly, the honeymoon period may be coming to a close. As Bernie Sanders becomes more popular, he will become seen as a genuine threat by Hillary Clinton and her powerful establishment backers. Originally, it appeared that Clinton hoped to win the Democratic presidential nomination by default, without having to compete much. Instead, she has been surprised by Sanders’ surging popularity and her own never-ending email scandal.

Clinton’s ascendancy to the Democratic nomination is no longer assured. Sanders now commands the lead in New Hampshire pre-primary polls and has closed to within seven points of Clinton in Iowa. Clinton has bungled her response to her private email server scandal, continually refusing to apologize and attempt to skirt the issue. Though many Democratic establishment loyalists, both voter and donor alike, continue to support the former Secretary of State, she has been wounded. The general public increasingly distrusts Clinton, viewing her as the second coming of Richard Nixon.

As Clinton struggles to maintain her lead, we Sanders supporters need to be prepared for her to go negative. Already, Clinton has lobbed some veiled jabs at her former U.S. Senate colleague, insinuating that the progressive phenom is a speech-making ideologue instead of a true “champion” of the people. Most of the attacks on Sanders, however, have come from Clinton’s lackeys: New York governor Andrew Cuomo, U.S. Senator Claire McCaskill (D-MO), and U.S. Rep. Joaquin Castro (D-TX). Eager to dance for the Clinton political machine, many prominent politicians will be encouraged to lob attacks at Bernie Sanders.

This is to be expected. Clinton is a uniquely powerful Washington insider, and her status as Democratic presidential frontrunner makes her a magnet for ambitious endorsers. They view her as the best chance to advance their own careers…or repay favors from the Bill Clinton presidency. Cuomo, for example, is a former Bill Clinton appointee. Castro, a young buck, is likely dreaming of a cabinet post. Countless other Clinton endorsers have either signed on to kiss the ring or repay a ’90s-era favor. Frankly, their blatant attempts to curry favor are rather transparent.

However, despite the transparency of Clinton’s ambitious puppets, their attacks will generate considerable press coverage and have the chance to harm Sanders’ growing popularity. How Sanders supporters respond will be important. Clinton’s camp clearly wants to goad Sen. Sanders (I-VT) into a fight, forcing him to shed his aura of wholesomeness. With her unlimited millions able to blanket media markets with attack ads, Clinton has an advantage in mudslinging…but can only unleash her attack lackeys freely if Sanders strikes back.

Thus far, Bernie Sanders has taken the high road. He has stuck to the issues and refused to criticize Clinton directly, despite prompting by the media. This has upheld his popular image while simultaneously denying Hillary Clinton an opportunity to drag the fight down into the muck. She is losing the fight over the issues, where Sanders’ bold and comprehensive policy proposals inspire millions, and wants to change the venue. A mudslinging takes the fight into the here-and-now, allowing pundits to ignore Clinton’s past flip-flops on important issues like same-sex equality, the Iraq War, and controversial criminal justice legislation.

When the attacks come rolling in, Sanders supporters must follow their candidate’s example and stick to the high road. We must explain the merits of his ideas and proposals, not lash back. Clinton’s camp is spoiling for a fight, and we must not give them an opening. We must expound on the merits of Sanders’ political history, his policy proposals, and his track record of immense integrity.

Sanders’ political resume is excellent, and he has more experience than Clinton. While Clinton has only served one elected position, that of U.S. Senator from New York, Sanders has executive experience as a mayor of Burlington, Vermont and has served in both houses of Congress. He has been running for office since the 1970s and was elected mayor in 1981, well before Clinton’s controversial 2000 campaign for a U.S. Senate seat from New York.

He pulled himself up by his bootstraps while Clinton was handed a U.S. Senate seat in a state in which she had never lived.

Sanders is not a flip-flopper, and the issue of Clinton’s flip-flopping could be a killer in the general election. In 2004, Democratic nominee John Kerry was wounded by the Bush campaign’s insinuation that he was a weak leader due to past reversals of decisions. Undoubtedly, Republicans will level similar charges at Clinton should she be the Democratic nominee.

Gentle reminders of Sanders’ political record should set the record straight. We must continue highlighting the importance of his proposed reforms and their international successes, especially when it comes to health care. Simply put, universal health care works…and at a fraction of the cost of America’s “free market” system where none of the market forces have worked to lower cost or improve either access or quality. Similarly, tuition-free higher education for qualified students also works. In Europe, college admissions are largely based on aptitude rather than ability to pay (or get unlimited government loans)…and they are producing college graduates with considerably better job skills than we are!

Bernie Sanders’ policy proposals are backed by worldwide data and have won the hearts of millions. Instead of taking the bait to go negative in response to attacks by Clinton or any of the many Republicans, we should simply highlight Sanders’ successes and the data that support his policies.