WASHINGTON — Joe Walsh, the ex-suburban Chicago GOP House member turned conservative radio talk show host, announced a long-shot primary challenge to President Donald Trump on Sunday — met with a giant shrug by the Republican establishment.

The bombastic Walsh, no innocent when it comes to incendiary language and race-based slurs against former President Barack Obama — newly repentant as he leads the charge against Trump — is casting himself as one of the few Republicans who believe — and who are willing to say in public — that the “Emperor Has No Clothes.”

Walsh, 57, is an admittedly flawed messenger when it comes to outrage over Trump, given his own record as a provocateur.

Walsh’s first quest for elected office was in 1996, when he ran against the late liberal lion Rep. Sid Yates, D-Ill., casting himself as a sort of liberal Republican in a district anchored on the left-of-center North Side Chicago lakefront.

After that defeat, Walsh eventually headed to the conservative northwest suburbs and took a sharp right turn. Riding the Tea Party wave in 2010, he defeated Rep. Melissa Bean, D-Ill., only to last one term, when he lost in 2012 to Tammy Duckworth, now the junior senator from Illinois.

In a 2011 interview, Walsh told me that he sees getting media attention as a major part of his job in Congress. “I came here figuratively to scream from the mountaintop.”

That’s still Walsh’s M.O.

Currently, Walsh earns his living as a syndicated conservative radio talk show host, though whether he can challenge Trump and keep that job is up in the air.

Walsh, a Mundelein resident, was in New York when we discussed his presidential race in a phone interview Sunday morning. We talked shortly after he kicked off his bid in an interview with host George Stephanopoulos on ABC’s “This Week,” timed to coincide with a the release of his announcement video.

His campaign slogan is “Be Brave.”

“I’ve been disappointed all year that no Republicans stepped up to challenge this guy who is unfit,” Walsh said. “So I wrote that (Aug. 14) New York Times op-ed piece as a plea for somebody in my party to step up. But nobody did. And it became clear to me this past week that nobody was going to step up to make the moral case against Trump. So I decided to step up and say to the world that he’s unfit,” Walsh told me.

What’s his plan, as he starts a national campaign from scratch?

“I’m going to go out every day and try to just pound Donald Trump and find the Republicans who are willing ... to say publicly what they believe privately,” Walsh told me. “And I believe the vast majority of Republicans believe, I believe privately that Donald Trump is unfit. So we’re going to be very aggressive. We’ll be in New Hampshire and Iowa. We’re going to be on TV as much as we can spreading this message,” Walsh said.

Walsh discussed a presidential campaign with leading GOP Trump critics William Kristol and George Conway, the husband of Trump top White House adviser Kellyanne Conway whose anti-Trump tweets have given him a following.

I asked Walsh what advice they gave him.

“The advice was that if you’re going to do this it’s a big deal … they both said you better make the moral case against Trump, how dangerous another four years of Donald Trump would be because this guy’s nuts and he’s a narcissist extraordinaire.

“So the same thing that I felt in my gut, Lynn, they affirmed, which is you don’t run on any issue, you run against Trump, who he is; it’s a referendum on Trump.”

Walsh is getting a burst of national attention though it’s not easy to leverage that into political support. Polls show Trump has the overwhelming backing of Republicans.

Trump campaign director of communications Tim Murtaugh brushed off Walsh’s entry into the primary in an email to the Sun-Times; when asked for a comment, Murtaugh responded: “Whatever.”

Richard Porter, a Republican National Committeeman from Illinois, told the Sun-Times that Walsh will have “no impact” on the primary. He added, “I think his only audience will be in the alternate universe of CNN and MSNBC viewers.”

Brian Baker, a spokesman for Todd Ricketts, who is running the fundraising drive to re-elect Trump in 2020, also had a one-word reaction to Walsh’s entry: “hilarious.”

Trump loyalist turned scorching Trump critic Anthony Scaramucci said in a Tweet, “May God be with you Joe. In an hour of darkness we pray for humility and courage.”

No matter where this leads, give Walsh credit for repudiating his race-baiting statements about Obama. Stephanopoulos asked, “Did you really believe he’s a Muslim?”

Said Walsh, “God no. And I have apologized for that. And that’s not an easy thing to do, not at all.”