Former House Speaker Newt Gingrich said Sunday that he’s open to being running mate to Donald Trump, the presumptive Republican presidential nominee.

"I don't think it's an automatic yes," Gingrich said on "Fox News Sunday." But “I’d be hard-pressed not to say yes,” under the right circumstances.

Gingrich -- who ran for president in 2012 and has been one of Trump’s biggest supporters within the so-called Washington establishment -- said he’d first have to discuss the issue with wife Calista and mentioned a commitment to publishing a book.

“We’re pretty busy, but we certainly could be lured into a new path,” said Gingrich, acknowledging that such questions arise about this time in a presidential election cycle.

"I don't know," he also said. "It's certainly a great challenge. But … I have a pretty interesting, exciting life."

Trump recently acknowledged that he now has five or six names on his list of potential vice presidential candidates and has said he will announce his decision in July, during the GOP nominating convention in Cleveland.

Gingrich also suggested Sunday that his decision would be based largely on what duties Trump would expect from a vice president and whether Trump indeed considers the job as “serious.”