WASHINGTON — I’ve been radicalized. By Harry Reid and Barack Obama. Goodbye moderation and sweet reason. No more clinging to constitutional and procedural restraint. It’s time to go nuclear.

In the fourth quarter of his presidency, Obama unbound is abusing presidential authority at will to secure a legacy on everything from environmental regulation to immigration, the laws of which he would unilaterally suspend.

Republicans find themselves on the sidelines bleating plaintively about violations of the separation of powers. They thought they found an instrument of resistance in funding for the Department of Homeland Security. The House has funded the whole department except for the immigration service, which was denied the money to implement Obama’s executive amnesty.

But Democrats have filibustered the bill in the Senate, where it will die. And as the night follows day, Republicans, not the filibustering Democrats, will be blamed for shutting down DHS and jeopardizing the nation’s safety at a time of heightened international terrorism.

A nice cul-de-sac. But there is a way out for the GOP. Go bold. Go nuclear.  Abolish the filibuster. Pass the bill and send it to the president.

I know that breaks a lot of china. But Congress is already knee-deep in fractured porcelain. On policy, Obama has repeatedly usurped congressional power, most egregiously with an executive amnesty for illegal immigrants that for four years he himself had insisted was unlawful.

As for procedure, Reid went nuclear in November 2013 when he abolished the filibuster for presidential appointees and judicial nominees (below the Supreme Court). He did it to pack the D.C. Circuit Court of Appeals with liberals. The nation’s liberal chorus cheered. “Elections are supposed to have consequences,” read one typical commentary. “It was time to push the button.” Boom.

My beef with Reid was not what he did but how he did it. The filibuster has grown in use and power over the decades to the point of dysfunction. Everything needed 60 votes. This is relatively new and nowhere to be found in the Constitution.

My problem was the egregious way Reid changed the rule: by a simple majority, 52-48, with zero Republicans onboard (and three Democrats defecting). As I wrote at the time, “If a bare majority can change the fundamental rules that govern an institution, then there are no rules.”

I was not the only one to warn that Democrats would rue the day. Once you go nuclear, so can the other guy.

Reid went first. Time for Majority Leader Mitch McConnell to finish the job. Push the button. Abolish the filibuster.

Then immediately pass the House homeland security bill and send it to the president. He is likely to veto it, but the politics will have been radically changed. The current storyline is: Republican Congress won’t fund DHS, threatening to shut it down. New storyline: Obama vetoes funding for DHS, threatening to shut it down.

The latter narrative is more accurate: Democrats are stopping the funding. Moreover, a presidential veto would lead to a more fair allocation of blame. And it’s blame allocation that determines which side blinks first. The president will have a major incentive to find some face-saving finesse.

But filibuster abolition is more than a one-shot proposition. It would radically change the next two years. It would give Republicans full control of the Congress and allow swift passage of a GOP agenda.

It would also clarify the antagonists: a lawless president vs. a willful Congress. The GOP could be sending bill after bill to the president’s desk — on tax reform, trade, Obamacare and, if it has the guts, immigration.

Obama’s choice? Sign, veto or negotiate a compromise. If he vetoes, then Republicans take that issue to the country in 2016.

What’s the downside? Democrats showed in 2013 their willingness to trash Senate procedure for a mess of pottage — three judges on one court. If Republicans stand pat now, what’s to stop Democrats from abolishing the filibuster altogether when it suits them in the future?

And think of the upside. A GOP resort to the nuclear option might make Democrats come to their senses and negotiate a new understanding that any fundamental change in Senate rules — e.g., altering the filibuster — will henceforth require some agreed to supermajority. No more bare-majority party-line coups.

This would be ideal. But that’s for later. For now, go for the doable. Abolish the filibuster and challenge the president. And when asked, “How can you do such a thing?” tell them to ask Harry Reid.

Charles Krauthammer’s email address is letters@charleskrauthammer.com.

(c) 2015, The Washington Post Writers Group