Stop whining about Democrats criticizing each other. The idea that Democrats attacking Democrats is a risk and an avenue that will deliver reelection to Donald Trump is nonsense. Democrats must attack each other and attack each other aggressively. Vetting presidential candidates, highlighting their weaknesses and the gaps in their record is essential to building a more qualified candidate.

The Democratic debate in Las Vegas was held at the Paris Hotel, but may well have been in the Grand Garden Arena at MGM as a heavyweight boxing match. The pre-existing belief about the debate was that five of the candidates would bombard Mayor Michael Bloomberg with attacks, and while Bloomberg took significant hits in the debate, each candidate took heavy fire. And they should. None of the candidates is perfect, and each has ideas, proposals, and positions that fall short of achieving the goals that he or she promises. Each also has a history with potholes and speedbumps. And while each Democratic candidate argues that Donald Trump is an ineffective candidate—at best—the reality is that the president is profoundly effective at identifying and highlighting the weaknesses of an opponent. It was true in the Republican primary campaign in 2016, it was true in the general election against Hillary Clinton, and it will be true again in the 2020 campaign.

Not only should Democrats welcome the attacks among candidates, but supporters of Democratic candidates should welcome the attacks on the candidates they support. If a candidate’s records and ideas are too weak or compromised to withstand criticism on a Democratic primary debate stage, that candidate will crumble under a barrage of television and radio advertisements from President Trump. President Trump will embarrass a Democratic candidate who has not faced a set of primary attacks.

Mayor Bloomberg faced attacks over his stop and frisk policies and a record of sexism. Mayor Pete Buttigieg and Senator Amy Klobuchar were attacked over their healthcare policies, and Klobuchar faced additional attacks over her record as a prosecutor and her knowledge of foreign policy. Senator Bernie Sanders endured criticism over the costs of his proposals and his promises to release his health records. Vice President Joe Biden was dinged over his positions on climate change.

Commentators, the twitterati, and others may describe the Democratic debate as a mess and a slaughter. Some may come away saying that the infighting may signal a party unready to take on the president’s reelection effort. Yet, the Democratic debate in Las Vegas was a masterpiece in what presidential campaigning should involve.

Mayor Bloomberg’s record around racial issues in New York and his Trump-style commitment to non-disclosure agreements are a liability among Democratic voters. Senator Sanders’s vilification of America’s wealthy seems at odds with the three homes he owns. A lack of detail in Senator Klobuchar’s healthcare proposals can leave Americans unsatisfied on a top-5 issue. Vice President Biden’s meek approach to the climate crisis seems disconnected from the demands of many Democratic voters. And while each of these issues may not be as critical of a liability when compared to the positions and history of Donald Trump, the president has an uncanny way of criticizing opponents for the very behaviors he has undertaken.

Candidates must acknowledge their weaknesses and either contextualize them properly or apologize for them completely. Wednesday’s debate clearly highlighted the work that Democrats need to do in preparation for the November contest. It should also highlight for every candidate’s supporters that no one’s record is perfect, and the canonization of candidates among their supporters must give way to a realistic reflection on their records.

Whether you are a Democrat or a Republican, you should welcome political debates that feature attacks. Such debates help inform voters, improve candidates, and strengthen the policy conversation. While the strongest candidate doesn’t always win, any candidate who endures a bruising primary debate emerges stronger for it. Some may come away from the Democratic debate in Las Vegas angry that their candidate was attacked. They should not. The Las Vegas debate—and the future debates—will ensure that whoever emerges as the Democratic standard-bearer will stronger for it.