President TrumpDonald John TrumpTrump says 'Failing New York Times' should be held 'fully accountable' over Russia report Trump says 'Failing New York Times' should be held 'fully accountable' over Russia report Trump tweets ICE will begin removing 'millions' of undocumented migrants MORE's supporters chanted “lock her up” ahead of his arrival at a rally in Mosinee, Wis., on Wednesday evening, just hours after the Secret Service said it found "potential explosive devices" in mail sent to former Secretary of State Hillary ClintonHillary Diane Rodham ClintonBroadway play 'Hillary and Clinton' closing early due to low ticket sales Broadway play 'Hillary and Clinton' closing early due to low ticket sales Facing challenge from Warren, Sanders touts strength against Trump MORE at her home in Chappaqua, New York.

Video of the rally showed the crowd chanting the phrase as Sen. Leah Vukmir (R) delivered remarks shortly before Trump’s scheduled appearance.

The chant, which has become a regular feature of Trump's rallies since his presidential campaign, came hours after authorities discovered potential explosive devices had been sent to Clinton’s New York residence, in addition to other Democrats including former President Obama, Rep. Maxine WatersMaxine Moore WatersFive memorable moments from Sarah Sanders at the White House Five memorable moments from Sarah Sanders at the White House Dems eye repeal of Justice rule barring presidential indictments MORE (Calif.) and former Attorney General Eric HolderEric Himpton HolderCongress and contempt: What you need to know Congress and contempt: What you need to know The Hill's Morning Report - Democrats wonder: Can Nadler handle the Trump probe? MORE.

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Each of those targeted by the suspicious packages have been criticized repeatedly by Trump, who condemned the attempted attacks as “abhorrent” during remarks from the White House East Room on Wednesday afternoon.

“We are extremely angry, upset, unhappy about what we witnessed this morning and we will get to the bottom of it,” he said.

White House press secretary Sarah Huckabee Sanders also said the president and administration officials are monitoring the developments.

"Our condemnation of these [despicable] acts certainly includes threats made to CNN as well as current or former public servants. These cowardly acts are unacceptable and wont be tolerated," she tweeted.

Clinton and other bipartisan lawmakers called for officials to dial back their rhetoric in response to the attempted attacks.

Trump was stumping for Wisconsin Gov. Scott Walker (R) in his reelection bid against state schools superintendent Tony Evers (D), and Leah Vukmir, who is challenging Wisconsin Sen. Tammy BaldwinTammy Suzanne BaldwinValedictorian says he was not allowed to use graduation speech to come out as gay Valedictorian says he was not allowed to use graduation speech to come out as gay Democrats highlight history-making LGBTQ lawmakers for Pride month MORE (D).

Walker is battling Evers in a tight race, which RealClearPolitics has dubbed a "toss-up." A RealClearPolitics average of polling gives Evers a 3.6 percentage point edge in the race. 

Baldwin has a double-digit lead over Vukmir, according to a recent Marquette Law School survey of likely voters.

--Updated on Oct. 25 at 7:33 a.m.