Rick Santorum tells Jay Leno why Mitt Romney endorsement was “buried” (VIDEO)

Former presidential candidate Rick Santorum explained to Jay Leno why he waited until late Monday night to endorse Mitt Romney in the 13th paragraph of an email to supporters.

In an appearance Tuesday on the "Tonight Show," the former Pennsylvania senator insisted he wanted his supporters to have the news first thing in the morning, the New York Daily News reported.

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Leno responded that he thought Santorum would have been in bed by 11 p.m. most nights.

"No, no. We have seven kids, so we don't sleep," a smiling Santorum said, outfitted in his signature sweater vest.

So why was the endorsment, "kind of buried," as Leno put it?

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Santorum said the message about him, not Romney, the Christian Science Monitor reported.

“This was a letter to my supporters — who were for me — to say, ‘Well, here’s now why I think we should rally around Mitt Romney and support him,’" Santorum said.

He added that he “has some concerns” which he wanted to discuss with Romney before formally endorsing him, ABC News reported.

“I voiced some of the things that I thought were important for us if we are going to be successful in this general election that he would take the cudgel and run with it,” Santorum said.

At one point during his campaign, Santorum called Romney the "worst Republican in the country" to put up against President Barack Obama. He told Leno he was speaking strictly about Obamacare, but trusted that Romney would work with Republicans in Congress to repeal it.