CNN  — 

It was no accident that two Iowa GOP icons – Chuck Grassley and Bob Dole – attacked Ted Cruz the day after Iowa’s Republican governor said a vote for the Texas senator would be bad for the lead-off caucus state.

It is part of a fascinating and once unthinkable calculation by leading establishment figures that Donald Trump is the lesser of two evils at the top of the Republican presidential pack – and defeating Cruz in Iowa is now part of this strategy.

To be sure, these establishment figures still worry that both Trump and Cruz would hurt Republican candidates down ballot. So why settle on Trump as the least objectionable of the two?

One leading GOP strategist involved in the effort put it this way: “If Trump loses we wash our hands of him. Cruz will think we need to be more crazy and be a long-term nightmare.”

Translation: Trump would be a one time worry, but Cruz, just 45, would likely blame the moderate establishment if he lost as the GOP nominee and run again – having had a national campaign to build a stronger organization.

Dole: Cruz worse for GOP than Trump

The decision for Dole, the party’s 1996 nominee and the Iowa caucus winner in 1988 and 1996, comes after urgent conversations and research by leading party figures as they have come to the realization in recent weeks that Trump and Cruz appear far more formidable than any of the handful of candidates more acceptable to the establishment.

The hope still is that one of those candidates – Marco Rubio, Jeb Bush, John Kasich or Chris Christie – somehow catch fire in the closing days of the New Hampshire campaign and emerge as a strong alternative. But with polling indicating those candidates could split the vote, and that Trump will win New Hampshire, these leading establishment figures have been debating their best course.

A new wrinkle in their research triggered the effort to defeat Cruz in Iowa.

Inside the Cruz campaign the goal is an Iowa win, a decent showing in New Hampshire and then more wins as the calendar turns South in March.

But new private polling conducted for a GOP establishment group shows Trump leading Cruz in several Southern GOP congressional districts. Those numbers of course could change if Cruz gets some wins and momentum, and as a result – the establishment decided to attack Cruz with new vigor in hopes of denying him an Iowa victory.

“It’s all about Iowa,” a leading establishment operative said when asked about the Dole attack.

READ: Ted Cruz’s no-good, very bad day

This and several other sources involved in the effort spoke only on condition of anonymity because of the sensitivity of the effort inside Republican circles.

Conservatives, meanwhile, are furious at the effort, noting that Trump has called himself both a Democrat and independent in the past, and Cruz deserves party loyalty despite issues differences.