Update: In an interview Friday morning with the Chicago Tribune, Walsh defended his tweet and said he wasn't trying to incite violence:

"Of course I didn’t mean ‘let’s go kill Obama and Black Lives Matter.’ I was not trying to incite violence against Obama and Black Lives Matter. That’s crazy and stupid and wrong."

He added: "There’s a war against our cops in this country, and I think Obama has fed that war and Black Lives Matter has fed that war. ... Obama’s words and the deeds of Black Lives Matter have gotten cops in this country killed.”

Walsh also told the Tribune he's been getting death threats on social media from "the left."

Whether he meant it or not, his latest comments are arguably some of the most controversial in the immediate aftermath of Dallas, so it's worth learning a bit more about him:

The basics: He's held public office only once, though he's run several times. He beat a Democrat to serve in Congress from 2011-2013 in a Chicago-area district that has bounced back and forth in recent years between Republicans and Democrats. He lost reelection to a Democrat and now hosts a conservative talk radio show.

He won his only general election by 291 votes: Walsh's thin win over a three-term Democrat — he beat her by 291 votes without the help of his party — was a surprise. It came during the 2010 tea party wave, when Walsh positioned himself as a conservative, anti-establishment Republican. (Perhaps unsurprisingly, that establishment spent no money to help him.)

He lost reelection two years later in a nasty and expensive nationally watched race against Iraq War veteran Tammy Duckworth. If her name sounds familiar, it's because Duckworth is currently challenging Sen. Mark Kirk (R-Ill.) for the Senate seat in what's expected to be a very tough race for the Republican incumbent.

He worked in inner-city Chicago before politics: Walsh taught at inner-city Chicago schools, including teaching high-school dropouts basic life skills, and ran a scholarship fund to pay for low-income Chicago students to attend private schools. Walsh also worked in venture capital, though he told reporters he never made much money.

He's pulled some "outrageous" stunts to get elected: In 1996, when Walsh won the Republican nomination to try to unseat longtime Democratic Rep. Sidney Yates in a neighboring, more liberal congressional district, his campaign grabbed headlines for, in Walsh's words, "some outrageous" stunts.

According to the New York Times, he offered $1,000 for the first person who could spot Yates in the district. He ended up paying Yates's doorman.

He campaigned on a bicycle and carried around an oversize check for $1,000, which he promised to donate to charity if Yates would debate him for an hour.

He also rented a hotel, invited hundreds of people and threw a birthday party for Yates, who was then 87. "The Congressman did not attend," the Times wrote. Yates won by more than 52,000 votes.

The Republican Party wasn't a fan: In that 1996 election, Walsh described himself as "moderate Republican."

"If there's a more gay-friendly Republican around, I'd like to meet him," he said. But when he successfully ran for office 14 years later later, he pitched himself far to the right of the national GOP.

When he won the six-person primary, the House Republicans' campaign arm in Washington told the Chicago Tribune it was essentially giving up on the race. Not even the state Republican Party spent money on the campaign, leaving Walsh badly outspent by his Democratic opponent, Rep. Melissa Bean. Nonpartisan election watchers in Washington ranked the race as "Safe Democrat."

Walsh ended up beating Bean by 291 votes in one of the closest results in the country, no doubt helped by the incredible Republican wave of 2010 that helped the GOP secure its largest post-World War II majority in Congress.

He's no fan of Obama: Almost immediately after arriving in Washington, Walsh started picking fights with Obama.

He posted a YouTube video accusing the president of bankrupting the country. His colorful language made him a favorite of cable news — "the biggest media hound in the freshmen class," my colleague David Weigel, then with Slate, wrote. In a 2011 interview with Weigel, Walsh claimed Obama was only elected president because he is a "black man who was articulate":

Why was he elected? Again, it comes back to who he was. He was black, he was historic. And there’s nothing racist about this. It is what it is. If he had been a dynamic, white, state senator elected to Congress he wouldn’t have gotten in the game this fast. This is what made him different. That, combined with the fact that your profession ... not you, but your profession, was just absolutely compliant. They made up their minds early that they were in love with him. They were in love with him because they thought he was a good liberal guy and they were in love with him because he pushed that magical button: a black man who was articulate, liberal, the whole white guilt, all of that.

He was kicked off air for racial slurs: Walsh's racially driven controversies didn't end with his time in politics. After politics he started a talk radio show, "The Joe Walsh Show," but it was briefly pulled from the airwaves after several racial and ethnic slurs on air during a discussion of the controversy over the team name of the Washington Redskins. Here, via the Daily Herald's Mike Riopell, is what he had to say:

Walsh is heard questioning why a CNN anchor could use the team name but wouldn't say an offensive term for African Americans. Walsh repeated the anchor's use of an outdated term for black people and the station abruptly went to a commercial. After a commercial break, Walsh said he was testing the radio station, using multiple words, and was setting up an offensive term for Latinos when the station abruptly went to commercial again.

Walsh said he was using the slurs to make an example of the media's double standard about what's acceptable to say — and not say.

His financial problems inspired a "deadbeat parents bill": Walsh has also had a series of financial struggles during his time in the spotlight. When he was running for office in 2010, he faced a lawsuit by his former campaign manager for not paying for services. While in office in 2011, Walsh's ex-wife sued him for more than $100,000 in back child support.

Following Walsh's headline-grabbing child support woes, the Illinois legislature debated a bill — dubbed the "deadbeat parents bill" — forbidding people who owe more than $10,000 in child support from running for office.

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