When you’re running for president, you want certain people in your corner.

Presumptive Democratic nominee Hillary Clinton used Sen. Elizabeth Warren’s star power to her advantage Monday in Ohio, as the two campaigned together for the first time. Hillary Clinton camp has many more troops in the reserves, highlighting another difference between presumptive Republican nominee Donald Trump and Clinton: The disparity between distribution of surrogates.

“There’s definitely a difference between the two parties and their use of surrogates this year,” said Marty Cohen, associate professor of political science at James Madison University and coauthor of “The Party Decides: Presidential Nominations Before and After Reform.”

Even without a Bernie Sanders endorsement, Clinton has plenty of big shots holding court on her behalf, including a Congressional surrogate program that regularly schedules supportive Senators, mayors and members of Congress for media interviews. This has helped her reach communities she may not be able to connect with herself and allowed her to compete with Trump, who will regularly give a half dozen interviews a day. Clinton’s campaign has also made the broad support a central part of her messaging.

In contrast, the last two Republican presidents have withheld support from Trump, and dozens of Republican leaders have been trying to distance themselves from their party’s nominee. “His inability to have those people in his corner is telling,” Jesse Ferguson, deputy national press secretary for the Clinton campaign.

But Trump has made up for this by casting his campaign as one that opposes the establishment of both parties. At campaign events and on cable television, he has elevated a list of once-minor activists to sound his clarion call. The list includes Scottie Nell Hughes, a chief political commentator for USA Radio Networks, Omarosa Manigault, a former The Apprentice contestant, Jeffrey Lord, who served in the Reagan White House, Katrina Pierson, a former reality television star and Sarah Palin, former governor of Alaska. During the primary, Trump also relied heavily on Liberty University’s Jerry Falwell, Jr. and former Indiana basketball coach Bob Knight. “Donald Trump is a hard person to be a surrogate for… He’s his own best advocate,” Cohen said, adding that it is difficult to add anything on top of Trump himself. “His style is so unique and can’t be substituted.”

There are other reasons Trump can be difficult to be a surrogate for.

Ryan Williams, a Republican strategist and former spokesman for the Mitt Romney campaign, said people balk at pulling surrogate duty for Trump because he makes statements that leave them having to “spin the impossible.”

The example Williams used was U.S. Rep. Lee Zeldin, a Trump endorser who said Trump made racist comments about Judge Gonzalo Curiel, who is presiding over a trial involving Trump University, but stuck with his endorsement.

“Presidential campaigns need surrogates. You cannot go it alone,” Williams told TIME, stating a campaign without surrogates is like trying to win a football game with half of the team missing.

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