In Wisconsin, supporters of President Trump attending a campaign rally in Mosinee were unmoved by someone mailing an explosive device to Hillary Clinton, chanting "Lock her up! Lock her up! Lock her up!" after Republican Senate candidate Leah Vukmir mentioned the former secretary of state's name.

Vukmir spoke ahead of Trump, and she smiled and laughed as the crowd chanted "Lock her up!" It's a refrain heard at almost every Trump rally, although typically the chants begin when Trump is onstage, having whipped the crowd into a frenzy. Trump came to Wisconsin to rally for Vukmir; a Reuters/University of Virginia Center for Politics poll released Wednesday has incumbent Democratic Sen. Tammy Baldwin 15 points ahead of Vukmir.

Explosives were sent to Clinton and several other high-profile Democrats, including former President Barack Obama, as well as CNN. Before leaving for the Wisconsin rally, Trump said the country needs to "unify, we have to come together, and send one very clear, strong, unmistakable message: That acts or threats of political violence, of any kind, have no place in the United States of America." Catherine Garcia

Former Vice President Joe Biden already racked up two Senate endorsements within an hour of entering the 2020 race.

Biden's long-awaited announcement that he is running for president in 2020 was quickly followed by an endorsement by Sen. Chris Coons (D-Del.), whose Senate seat was formerly held by Biden. Coons in a statement says that Biden "doesn't just talk about making our country more just, he delivers results."

After Coons' endorsement came one from Sen. Bob Casey (D-Pa.), who said that Biden "has delivered results for the middle class, kept our country safe and strengthened our standing in the world."

Biden is the only 2020 Democratic candidate who has been endorsed by more than one U.S. Senator, according to a tally by FiveThirtyEight. Previously, Sens. Elizabeth Warren (D-Mass.), Amy Klobuchar (D-Minn.), Cory Booker (D-N.J.), and Bernie Sanders (I-Vt.) each received an endorsement from one of their Senate colleagues.

More Senate endorsements look to be on the way for Biden, with Sens. Dianne Feinstein (D-Calif.) and Thomas Carper (D-Del.) having signaled they will back him. Politico previously reported that Biden was "planning to solidify his front-runner status with a wave of high-profile organizing, fundraising and endorsement news when he enters the race."

One endorsement Biden didn't receive on Thursday, however, was that of former President Barack Obama. A statement from Obama's spokesperson praises Biden's "knowledge, insight, and judmgent" but stops short of endorsing him. CNN's Jeff Zeleny reports Obama has no immediate plans to endorse any candidate, as he wants them to "make their cases directly to the voters." Brendan Morrow

Joe Biden kicked off his presidential campaign on Thursday as the clear frontrunner not only in the Democratic field but also the general election, according to Politico/Morning Consult polling. In a head-to-head contest with President Trump, Biden draws 42 percent to Trump's 34 percent, an 8-percentage point lead that puts Trump in a much worse position than former President Barack Obama when he was running for re-election in 2012. Morning Consult conducted the poll April 19-21 among 1992 registered voters; the poll has a ±2-point margin of error.

Biden is ahead of closest Democratic rival Sen. Bernie Sanders (I-Vt.), 30 percent to 24 percent, in Morning Consult's weekly tracking polls. Biden and Sanders are followed by South Bend Mayor Pete Buttigieg (9 percent), California Sen. Kamala Harris (8 percent), Massachusetts Sen. Elizabeth Warren (7 percent), and Beto O'Rourke (6 percent). The tracking poll covers April 15-21, is based on 14,336 interviews with Democratic primary voters, and has a margin of error of ±1 percentage point.

Biden's coalition is older, more racially diverse, and more moderate than Sanders voters, Morning Consult found. Biden just edges out Sanders in favorability ratings, though his net favorability dropped 5 points from January, a period in which he was accused of inappropriate handsiness. Peter Weber

Former Vice President Joe Biden announced in a video Thursday morning that he's making a third bid for president. Unlike in 1988 and 2008, though, he starts out as one of the frontrunners in a diverse field of 19 other Democrats. In a conference call with donors on Wednesday, Biden stressed the importance of notching strong fundraising numbers in the first 24 hours of his campaign, Politico reports. But in his launch video, Biden steered away from the prosaic, vowing to protect the core values and ideals that America stands for from President Trump, centering his pitch on Charlottesville, Virginia,

Biden, 76, starts out with strong name recognition, support from organized labor and other Democratic constituencies, and strong ties to former President Barack Obama, who is not endorsing anyone in the Democratic primary. He is expected to officially kick off his campaign at a Pittsburgh union hall on Monday. Peter Weber

"Like all of [President] Trump's closest relationships, his relationship with Twitter is sort of a love-hate situation," Trevor Noah said on Wednesday's Daily Show. And on Tuesday, Trump invited Twitter CEO Jack Dorsey to the Oval Office to complain. "That's right, my friends, the president of the United States is upset because he feels he should have more Twitter followers," Noah said. "This is absolutely ridiculous. Like, what's next? He's going to complain to Instagram because his thirst traps aren't blowing up?"

Trump flying in the CEO of Twitter to complain about losing followers will actually probably "inspire more people to run for office," Noah suggested. "People are going to be on stage, like, 'I'm running for president so that I can ask Jeff Bezos: What happened to my tube socks, which were supposed to be here by Wednesday?!'" He pitied "everyone in this meeting with Trump who had to sit there and take it seriously," including Dorsey, forced to "explain to a president that some of his followers were deleted because they were bots and spam accounts."

"Twitter is only one of the president's beefs right now," Noah said. He's also feuding with the media, House Democrats, and the Constitution, threatening to "head to the Supreme Court" if Democrats impeach him. "Just to be clear, that's not a thing," Noah said. "The Supreme Court can't overrule an impeachment. ... This would be like if a cop gives you a ticket and your response is: 'I'm fighting this, buddy — you'll be hearing from my orthodontist!'"

"So in the last 48 hours, the president has gotten in fights with Congress, the press, and Twitter," he said. "Look, we can't help him with the first two, but we do have someone who can help him out online." That would be Jaboukie Young-White, and you can watch him advise Trump to seem less thirsty on Twitter below. Peter Weber

President Trump made some promises during the 2016 campaign: He would release his tax returns, "build the wall," "drain the swamp," protect Medicare and Social Security, and champion law and order, to name a few.

Like all presidents, he has been pretty selective about which campaign promises merit follow-through. The "wall", for example, was worth shutting down the government and sparking a constitutional crisis; his tax returns were deemed worthy of going to court and threatening a constitutional showdown to keep hidden. One of the "promises" he has tried to keep, according to Special Counsel Robert Mueller's report, is "lock her up," his enduring campaign chant about 2016 rival Hillary Clinton.

Mueller's report "brimmed with examples of Mr. Trump seeking to protect himself from the investigation," The New York Times reports, but it also shows at least three instances of him "trying to wield the power of law enforcement to target a political rival, a step that no president since Richard M. Nixon is known to have taken." As with many potential crimes Mueller records, Trump's orders or suggestions to prosecute Clinton were apparently ignored or redirected by former Attorney General Jeff Sessions and former White House Counsel Don McGahn.

Still, Trump's attempt to target Clinton "reeks of a typical practice in authoritarian regimes where whoever attains power, they don't just take over power peacefully, but they punish and jail their opponents," political historian and professor Matthew Dallek tells the Times. It appears from Mueller's report that Trump, encouraged by his Fox News allies, didn't appreciate the difference between political self-preservation and weaponizing the law enforcement tools he seems to think work for him, adds Duke University law professor Samuel W. Buell. "All of his demands fit into a picture that he believes the apparatus is mine"

You can read the details of Trump's attempts to "lock her up" in Mueller's report and at The New York Times. Peter Weber

George Conway was, by all accounts, happy when his wife, Kellyanne Conway, helped campaign-manage President Trump into office. But that was so 2016. Since then, Conway has become one of Trump's loudest conservative critics, to the consternation of his wife, who is one of Trump's top White House aides and most ardent defenders in the media.

When Trump's 2016 rival, Hillary Clinton, wrote an op-ed in The Washington Post on Wednesday night, arguing that Vladimir Putin is trying to make Russia great again by attacking U.S. democracy and Congress needs to hold Trump accountable for aiding him, using Special Counsel Robert Mueller's newly released report as a road map, George Conway repurposed Clinton's 2016 slogan: "If she's with the Constitution, I'm with her. "

Ouch. Peter Weber