If you had to come up with a description for the response of institutional Republicans to Donald Trump, it would be this: Too late.

At every turn, Republicans have been late to challenge Trumpism. Back in August, as Trump was just taking over the race, Right to Rise’s Mike Murphy famously explained, "If other campaigns wish that we're going to uncork money on Donald Trump, they'll be disappointed. Trump is, frankly, other people's problem." Right to Rise did a fine job of holding down Marco Rubio's numbers by spending $35 million in ads against him. Because negative ads work. By the time they got around to spending $25,000 against Trump—not a typo—it was too late.

Jeb Bush could have hurried along the consolidation of votes against Trump by bowing out of the race after clocking in at 2.8 percent in Iowa and 11 percent in New Hampshire. Instead, he hung around to suck up 8 percent of the vote in South Carolina, denying Cruz and Rubio a shot at beating Trump. Too late.

The Republican donors who pumped Right to Rise full of money could have bankrolled a serious anti-Trump Death Star PAC in January and could have then used the money to bury Trump after Iowa, when he was vulnerable and Republicans were (foolishly) telling themselves that the nightmare was over. Instead, the Republican money didn't start to hammer Trump until after Super Tuesday on March 1. Too late.

After the bottom dropped out of Marco Rubio's campaign on March 5, Rubio could have gotten out of the race and cleared the way for Cruz. Instead, he stayed in and cost Cruz North Carolina and Missouri. Too late.

And now Republicans might be late again. Arizona and Utah vote next week. Ted Cruz should win Utah handily. Arizona is very much in play. Republicans and the Cruz campaign—and at this point, those two groups are practically synonymous—ought to throw everything they have at Arizona, because closing down Trump in the first (almost two-man contests) will:

1.) Deny Trump another 98 delegates, lowering further the probability of Trump getting to the 1,237 majority.

2.) Shift the momentum and narrative of the race.

3.) Freeze in place any wavering Republicans who are contemplating capitulation.

Four of the tools at Cruz's disposal should be Marco Rubio, John McCain, Jeff Flake, and Gary Herbert. The senators and Utah governor ought to endorse Cruz and they ought to do it five minutes ago.

There are plenty of bad reasons for Rubio and McCain, at least, not to endorse Cruz before Arizona votes: Maybe there would be blow back and it would give Cruz the stench of establishment. McCain has his own primary challenge to deal with. If they endorse and Cruz loses Arizona, then the endorsements were wasted.

But as I said, those are all bad reasons to hold off on the endorsement. The reason to go for it is simple: You play to win the game.

The reason Republicans have been too late to counter Trump at every turn is they have been on the defensive the entire time. Early in the race, this was the result of a collective action problem early in the race. Now it's because they're failing a test of nerve.

But they should note that there has been one period in the campaign—just one—in which Republicans carried the initiative and took the fight to Trump. It began at the February 25 debate where Cruz and Rubio took a flamethrower to Trump, mocking him, belittling him, and exposing him as a con artist. They carried on this attack on the stump and through the next debate, on through the March 4 debate. The attacks on Trump were relentless.

From February 1 through February 23, Trump won 3-of-4 states (and 61.6 percent of the available delegates).

On February 25, Rubio and Cruz began the assault on Trump.

In the Super Tuesday states on March 1, Trump won only 7-of-11 (and 36 percent of the delegates).

In the March 5 contests he won just 2-of-4 states (and 34 percent of the delegates).

But then the conventional wisdom kicked in and a consensus formed around the idea that all of the nasty, personal attacks on Trump had somehow backfired. That it was harmful for Rubio and Cruz (but especially Rubio) to sink to Trump's level. So they backed off.

And in the March 8 and March 15 contests, Trump rebounded, going 6-for-9.

The lesson here isn't that Cruz should go back to scorching Trump (though maybe he should), but rather that if you want to beat Trump you have to take the initiative.

Having Rubio, McCain, and Flake (and Herbert) endorse Cruz immediately is a start. It won't win Arizona by itself, but it would signal that Cruz isn't playing Arizona for expectations—he's playing to win. There should be no "too late" this time.