Laura Ingraham is returning to Fox News on Monday night -- but some of her advertisers are not.

The 10-day-old ad boycott effort against Ingraham, led by student activist David Hogg, means that her show will have noticeably fewer ads than other Fox talk shows.

While the exact impact is not known, a Fox source confirmed that some of the network's regular advertisers are continuing to avoid "The Ingraham Angle." The result is lighter ad loads during her hour.

The controversy started when Ingraham mocked Hogg on Twitter. Hogg, in turn, urged his followers on social media to contact Ingraham's advertisers.

All of a sudden there were headlines like "Laura Ingraham's taunt of David Hogg is just the latest attack on Parkland survivors."

Ingraham apologized for the tweet, but at least a dozen prominent advertisers distanced themselves from her program.

Related: Are TV ad boycotts the right way to protest?

Data from the tracking firm Kantar showed that "The Ingraham Angle" averaged 14 and a half minutes of ads up until the Hogg controversy. It dropped to eight minutes, 45 seconds of ads on the first night of the boycott, and to about seven minutes of ads on the second night.

That's when Ingraham announced a week-long vacation.

The network said it was a pre-planned spring break vacation with her children, but it doubled as a natural cooling-off-period for the controversy.

The vacation announcement sparked speculation about Ingraham's future, given the parallels to the Bill O'Reilly case exactly one year ago. O'Reilly, too, went on vacation amid an ad boycott -- and he never returned to the network.

But O'Reilly was facing damning headlines about secret settlement payments to women who had accused him of harassment.

In Ingraham's case, Fox decided to very publicly stand by her.

This is partly because 21st Century Fox patriarch Rupert Murdoch doesn't want his channel to give in to endless boycott campaigns. Vanity Fair reported that Murdoch instructed Fox News co-president Jack Abernethy to issue a supportive statement after the boycott picked up steam. "Sources say Murdoch has told people that Fox's current management has been too quick to cave to the network's many critics," Vanity Fair's Gabriel Sherman wrote.

Abernethy's statement last Monday quashed talk about whether the ad boycott would make her vacation permanent.

"We cannot and will not allow voices to be censored by agenda-driven intimidation efforts," he said. "We look forward to having Laura Ingraham back hosting her program next Monday when she returns from spring vacation with her children."

In situations like this, some advertisers simply shift their ads to other shows on the network. Others pull back on their ad spending altogether, at least temporarily.

The ad boycott's staying power remains to be seen. The other outstanding question: Will Ingraham address the matter when she returns to work?

A Fox spokeswoman declined to comment on Sunday.