DES MOINES, Iowa — Ted Cruz is out with a new ad attacking Donald Trump's "New York values." The ad includes a 1999 video of Trump saying he was pro-choice, and it also replays Trump's notorious "How stupid are the people of Iowa?" line from a speech in Fort Dodge last November, when Trump mused on how Iowa voters could possibly support the now-faded candidacy of Ben Carson.

It's an effective attack. And now, it highlights how critically important, and perhaps downright fortuitous, it was for Trump to arrange an appearance a few days ago with Chuck Grassley, Iowa's highly respected Republican senator who might just as well be known as Mr. Iowa Values. Thanks to Grassley's evenhandedness, Trump has an effective comeback to Cruz's attack.

It's an understatement to say heads were turned Saturday when Grassley showed up with Trump at a Trump rally in Pella, Iowa. "We have an opportunity once again to make America great again," Grassley said. "I want Mr. Trump to know that I appreciate his support for me and most importantly for Iowa being first in the nation, our all-important Iowa caucus."

Was Grassley, the most revered politician in the state, endorsing Donald Trump? Early reports sounded like it; one well-connected Iowa Republican told me he was "dumbfounded" when he heard the news.

But no, Grassley did not endorse Trump. The senator has, in fact, offered to appear with all the GOP candidates at their events, and will do so before next Monday's caucuses. Still, in the superheated context of the Iowa campaign's final week, Grassley's evenhanded decision to appear with the Republican front-runner may be more valuable to Trump than the others. As Monday nears, Trump's opponents — not just Cruz — are trying to convince Iowa Republicans that Trump is not one of them, that he doesn't share Iowa values, and that he would be a dangerous choice. The photo of Grassley onstage with Trump says just the opposite. If Trump is OK with Grassley, well, what's the problem?

The recent appearances were a long time in the making. In 2015, as candidates began to come to Iowa, Grassley offered to appear with anyone who wanted him. That year, Grassley showed up at events for Jeb Bush, Chris Christie, Ted Cruz, Carly Fiorina, Mike Huckabee, John Kasich, Rand Paul, Marco Rubio, Rick Santorum, Lindsey Graham and Scott Walker. Grassley's intention was not to promote any single candidate but to emphasize the importance of the Iowa caucuses in the Republican electoral structure. Iowans are constantly worried about losing their first-voting status, and Grassley wants to make sure Iowa remains a critical part of the process.

Last week, one of the candidates — it's not clear which one it was — requested that Grassley attend a campaign event. To be fair, Grassley then sent an offer to all the campaigns, saying he would appear with them in the last week before the caucuses.

The Trump campaign asked for an appearance. And so did Cruz, Rubio, Bush, Kasich, Christie and Carson — they're all booked for coming days. (Santorum and Paul are still being scheduled.) Grassley didn't announce the schedule, feeling it was up to the campaigns to decide when to announce their own events.

As it happened, Trump came first. And since there had been no announcement that Grassley's Trump appearance was the first of many appearances with all the candidates, the impression was left that Grassley had endorsed Trump without formally endorsing Trump.

"When Grassley said, 'We have an opportunity once again to make America great again,' using Trump's slogan, every Iowan in the room knew what he meant, even if it came with a wink and a nod," wrote Iowa journalist Robert Leonard, in a piece in Salon headlined, "I just watched Donald Trump win the Iowa caucus."

That's not what Grassley intended. "With Sen. Grassley there are no dog whistles or subliminal messages," chief of staff Jill Kozeny told me in an email exchange. "He says what he means and means what he says. Sen. Grassley told Republican candidates last year he'd like to introduce them to Iowa and Iowans. Candidates took him up on it. The offer was repeated last week, and he's on the campaign trail before caucus day. He offered to campaign with all, and he is. Simple as that."

Indeed, remember that Grassley's thanks to Trump was for supporting "our all-important Iowa caucus." For Grassley, it's all about Iowa.

Still, in the end, Trump received Grassley's imprimatur, sort of. And now, when Cruz attacks Trump's "New York values" and tries to set Trump apart from Iowa, Trump can point to Mr. Iowa Values himself.