No one has been more incisively critical of the Republican Party in Congress than Texas Senator Ted Cruz, though he has not been alone. In many ways, Republican capitulation and cooperation with Big Government forces spawned the Tea Party, and then, the candidacy of Donald Trump (albeit around different issues).

If the RNC and Republicans on Capitol Hill are to regain credibility, repentance must come first. The word means a 180-degree turnaround, and it starts with acknowledging failure. No single action would more clearly signal a GOP about-face than to nominate their chief critic — Ted Cruz. (I’ll explain why that’s better than the alternative in a moment.)

After the punishing 2012 presidential loss, the RNC made a show of performing an “autopsy” on itself — an absurdity of the highest order. Dead men are peculiarly incapable of self-reflection. But good intentions, and diagnostic white papers, are not the same as good medicine.

The Republican Party now stands on the edge of night. Only an obscurantist would continue whistling past the graveyard. The question remains what to do about it.

In 2013, Democrats shut down the federal government from October 1st-to-16th when they refused to pass a continuing budget resolution that defunded Obamacare. Of course, the mainstream media remembers this as the time when then-freshman Sen. Ted Cruz shut down the government. Indeed, Cruz was among the most vocal conservatives on Capitol Hill aiming to fulfill campaign promises to defund the ironically titled Affordable Care Act. GOP colleagues decried and mocked Cruz, calling him naïve. In hindsight, I’m sure Cruz agrees he was naïve to believe Republican senators meant what they told voters.

Republican leaders caved to Democrats mid-month, acknowledged defeat, and laid it at the feet of Cruz and his ilk. Obamacare blundered on its tragic way, bending the cost curve upward, driving medical professionals into retirement, and stripping people of family doctors.

Of course, Republican senators were right that the shutdown was a bad tactic, because the plan Cruz passionately advocated depended upon Republicans to stand against Obamacare in a more-than-symbolic fashion.

But while colleagues accused him of self-aggrandizing showmanship, Cruz understood more about negotiating from weakness than any of them did.

The opponent must be convinced that you won’t blink. Democrats didn’t defeat his plan. Republicans did, and then crowed about the wisdom of their prophesy, which was merely self-fulfilling. Republicans didn’t just blink, they batted their eyes alluringly at President Obama and their “friends” across the aisle. Together, they crushed the plan to crush Obamacare in a bipartisan manner, and they replaced it with…well, nothing. They didn’t have a plan to defund Obamacare; nothing but words on a mailer, slogans in a robocall, applause lines in a stump speech. Lip service.

Politicians and pundits cried that Cruz’s radical government-shutdown tactic would decimate the party in the 2014 mid-term elections. Indeed, a contemporaneous Washington Post/ABC News poll showed that 4-in-5 Americans objected to the shutdown, and 53 percent blamed Republicans. Democrats on the campaign trail crowed that Republicans were the government-shutdown party.

But the November 2014 election outcome startled them.

Republicans had a net gain of 13 seats in the House and nine in the Senate. Sen. Harry Reid got demoted to minority leader. In addition, Republicans picked up more than 300 state legislative seats, in every region of the country, as Democrats lost their stranglehold on a number of state governments. Before November 2014, Democrats enjoyed single-party control (legislature and governor) in 15 states — afterward, in just seven.

Did GOP leaders acknowledge the wisdom of Cruz? Not on your life. They doubled down on marginalizing Constitutional conservatives.

It’s not too late for the GOP to say: “We blew it,” and to get back to the fundamentals. Nominating Ted Cruz is not THE solution, but it is a demonstration of the solution, which must be broad, and deep and lasting if it’s to mean anything.

In effect, the party can say, “We nominated our biggest critic. We know that it’s not Republican principles that have hampered our credibility, but it was our failure to doggedly and consistently pursue those principles and to turn them into policy.”

Of course, no person likes to admit failure, but whether the party nominates Donald Trump or Ted Cruz, the choice is a de facto: “We blew it.”

With a Cruz nomination, the party would say: “We blew it by straying from the Constitution and playing the Democrats’ game by their rules.”

The Texan’s greatest slogan is that he wants to make the federal government small enough to fit inside of the Constitution. That’s precisely the right message. Republican principles are correct, and it’s time we started living, and governing, by them.

A Donald Trump nomination, on the other hand, would say: “We blew it on fundamental principles more than a century ago. It’s not that we failed to implement Republicanism, it’s that Republicanism is a failed ideology, so we nominated a man who’s ignorant, and dismissive, of our core principles.”

Trump would take the GOP in a direction antithetical to its roots, to its values and to its long-term viability. The party of liberty would become the party of protectionism, market manipulation, regressive taxation, eminent domain takings, rule of man over rule of law, and of bellicose ignorant bloviation.

One way or the other, the party fails and falls.

The only question: will it continue in name only, or will it rebuild on a Constitutional foundation of liberty?