Coming off a dismal showing in the New York primary, Ted Cruz found some inspiration in an unusual source on Tuesday night, likening himself not only to that familiar conservative icon, Ronald Reagan, but also to the closest thing liberals have to a patron saint. “Jack Kennedy looked forward instead of back to the first half century of world war,” Cruz told supporters at the National Constitutional Center in Philadelphia. “He knew that America could dream and build if we were set free—not tanks for war, but rockets for exploration.”

What could possibly have led Cruz, who’s run his entire campaign as the ultimate spokesperson for the Tea Party brand of “consistent conservatism,” to suddenly try fashioning himself as a new JFK? Simple: He can’t win the next crucial primaries running only as himself. In Maryland and Pennsylvania, the biggest states where Republicans vote next Tuesday, Cruz’s brand of “just say no” Republicanism is a hard sell.

But, please. This is Ted Cruz, the conservative firebrand who perturbs senators, actresses, and college roommates alike, a man so polarizing that Republican Representative Peter King told Morning Joe this week he would rather eat cyanide than live in a country that elected the Texas senator to the White House. You could hardly imagine someone further removed from handsome, charismatic, forward-looking JFK.

Cruz is far from the only 2016 presidential contender who’s tried to steal some thunder from a popular former president with whom he has little, if anything, in common. With the notable exception of Hillary Clinton, all the remaining candidates have tried to broaden their appeal by latching onto legendary commanders-in-chief, both in their stump speeches and their campaign ads. The historical figures they choose to reference are sometimes far-fetched, but always telling—not of the candidates’ strengths, but their shortcomings. These aspirational presidential analogies are intended to obscure and neutralize their weaknesses as a candidate—Cruz’s lack of charisma and a compelling vision, for instance. It’s a desperate strategy that is almost always doomed to fail.

This past weekend, with Bernie Sanders fighting desperately to catch up to Hillary Clinton in New York, his campaign released a new ad called “Sons of New York.” It begins with grainy footage from the Great Depression: men in bowler hats and overcoats filing through a soup-kitchen line, industrial workers in coveralls, and that other great twentieth-century Democratic stalwart, Franklin Delano Roosevelt, pontificating from a podium rigged up with NBC microphones. “Even when the deck is stacked, a New Yorker will find a way to break up big banks, create millions of jobs, and rebuild America,” a narrator says. “Some say it can’t be done again. But another native son of New York is ready: Bernie.” Through the magic of editing, the final shot shows Sanders and Roosevelt together on screen, gesticulating in the same wild way from their podiums.