An anti-Trump Republican group is launching new ads urging senators to call witnesses as part of the impeachment trial that's kicking off in the Senate.

Republicans for the Rule of Law is spending $1 million to air two ads on “Fox & Friends” and “Lou Dobbs Louis (Lou) Carl DobbsSean Hannity and Lou Dobbs to be deposed in Seth Rich lawsuit: report Trump praises several Fox News shows at briefing for coverage of Russia probe GOP leader says he doesn't want Chamber's endorsement: 'They have sold out' MORE Tonight” every day next week, the group announced Thursday.

The ads center on letting former national security adviser John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE testify. Bolton said earlier this month he would be willing to testify if subpoenaed.

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One ad uses clips of House GOP members lamenting a lack of first-hand witnesses as part of the impeachment hearings.

“Now, John Bolton, a witness with first-hand information, has agreed to testify in the Senate trial,” the narrator of the ad says. “Senate Republicans, Americans deserve the truth. Let Bolton testify.”

The second ad similarly focuses on Bolton’s knowledge of the administration’s decision to withhold aid to Ukraine, the issue central to allegations of President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE’s impeachment, urging senators to call the former official to testify.

In addition to the TV ads on the Fox shows, Republicans for the Rule of Law will promote the ads across digital platforms for the next two weeks in Utah, Arkansas, Maine, Tennessee, Colorado and Arizona.

Digital billboards with a similar message will also appear in each of the targeted states' capitals for the next two weeks.

The billboards ask, "What is Trump Hiding?"