President TrumpDonald John TrumpGraham to introduce resolution condemning House impeachment inquiry Support for impeachment inches up in poll Fox News's Bret Baier calls Trump's attacks on media 'a problem' 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 ClintonThe Memo: Trump 'lynching' firestorm is sign of things to come Hillary Clinton has said she'd consider 2020 race if she thought she could win: report Nielsen on leaving Trump administration: 'Saying no and refusing to do it myself was not going to be enough' 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 WatersOn The Money: Waters clashes with Trump officials over 'disastrous' housing finance plan | Dems jump into Trump turf war over student loans | House passes bill targeting anonymous shell companies House passes bill taking aim at anonymous shell companies Avoiding the snake in the grass: Let's not allow impeachment to divide us MORE (Calif.) and former Attorney General Eric HolderEric Himpton HolderSupreme Court throws out challenge to Michigan electoral map Amash: Trump incorrect in claiming Congress didn't subpoena Obama officials We can't allow presidents and public opinion to further diminish the work of the press 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 BaldwinFederal funding for Chinese buses risks our national security Democrats threaten to withhold defense votes over wall The Trump downturn: Trouble ahead for the US economy 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.