Across the Democratic presidential field, candidates are reading up on points of contrast with key rivals and preparing attack lines, while some are going a step further and simulating debate-stage cross-talk with staffers, practicing ways to butt into the conversation and create a memorable moment. Campaigns are studying how CNN handled past primary debates, when the hosts teed up opportunities for GOP candidates to criticize each other in 2015…

“If they’re going to make the [debates] in September, you need to make a move right now,” said Tom McMahon, the former executive director of the DNC. To do so, candidates must decide which opponents are “impeding their path to the nomination and draw a contrast with them that elevates their own candidacy in the minds of those like-minded voters that could be willing to break your way.”

The Democratic National Committee ratcheted up its criteria to appear on the third debate stage in Houston in September. Candidates must register at 2 percent in four approved polls and receive donations from 130,000 individual contributors. Just seven Democrats in the sprawling field — Biden, Harris, Sanders, Booker, Sen. Elizabeth Warren, South Bend, Ind., Mayor Pete Buttigieg and former Rep. Beto O’Rourke — have qualified so far, and the other dozen candidates want to change things fast, before the traditional quiet stretch in August. On Monday, businessman Andrew Yang also said that he had qualified for the third debate.