WASHINGTON — Now a conservative radio talk show host, former Rep. Joe Walsh, R-Ill., is “seriously” looking at a 2016 Senate run against Republican Sen. Mark Kirk. Walsh told me that Kirk, recovering from a stroke, has to show voters he is physically “capable” to keep doing the job.

“I am looking at it very seriously. I have given myself a month or two with which to make up my mind and we’ll see. I should know by early April,” Walsh told me in a telephone interview.

Kirk was elected to the Senate in 2010 after serving five terms in the House. On Jan. 21, 2012, he suffered a massive stroke and did not return to the Capitol until almost a full year later in 2013. He gets around the Capitol mostly in a wheelchair, and he uses a cane on the Senate floor.

“I think that myself and any Republican voter in this state has questions about Sen. Kirk’s health, similar to if he were running a business and we’d want to know that he’s in condition to run that business,” Walsh said.

“. . . I think it’s up to him to provide whatever medical information he needs to provide to show that he’s capable of doing this job, that’s all.”

Walsh is the first Republican to surface to consider challenging Kirk in the March 2016 GOP Senate primary. If he runs, Walsh will be coming at Kirk from the hard right.

Walsh, 53, said he would give up his show at WIND-AM (560) in Chicago and WNYM-AM (970) in New York if he ran. He told me that’s how he makes his living now.

The outspoken, controversy-courting Walsh is considering a comeback after serving a term in the House, defeated by Rep. Tammy Duckworth, D-Ill., in 2012. The Hill first reported his interest in the contest. Duckworth is also weighing a Senate run.

While conservatives have their issues with Kirk – a national security hawk and a social moderate who is willing more than most of his GOP colleagues to at times cross the aisle – so far, until Walsh, pragmatism has trumped philosophical divides when it comes to Kirk.

That’s because Kirk’s moderate reputation helps him in general elections in Illinois.

The conservative movement is not monolithic. Walsh comes from the Tea Party wing. David McIntosh, the president of a major conservative group, the Club for Growth, told me they are not active in trying to dump Kirk.

They have other fish to fry.

In any case, “To my knowledge, nobody from Illinois has come to us,” McIntosh said when I asked him about Kirk a few weeks ago at a breakfast hosted by the Christian Science Monitor.

I asked Walsh why he wanted to run against Kirk.

“Mark Kirk’s a liberal Republican and I’m a conservative Republican. We’ve always gotten along and the Republican party’s a big tent and all that, and I think last year was a watershed moment when Mark Kirk put his arms around Dick Durbin and refused to help Jim Oberweis, a fellow Republican, beat Durbin,” Walsh said.

What Walsh is talking about: Kirk said in March 2014 that he wanted to “preserve” his relationship with Sen. Durbin, D-Ill., and not engage in a “partisan jihad” against him because the two got along and worked well together. Taking a pounding from conservatives, Kirk reversed himself and said he would help defeat Durbin.

Kirk did end up helping Oberweis but did very little.

But it was enough that Durbin will not have to honor the nonaggression pact Kirk offered — and took back — in 2014.

I emailed and called Kirk’s spokesman for a comment but never heard back.