Donald Trump’s Affinity for Ted Cruz May Soon Be Changing

Donald J. Trump has been unyielding when it comes to trying to pinpoint the weaknesses of his top rivals for the Republican presidential nomination and exploiting them to no end. Except when it comes to Senator Ted Cruz.

“Well, I like him,” Mr. Trump said of Mr. Cruz in an interview with the radio host Laura Ingraham last week. “He’s backed everything that I said.”

That could soon change. A new poll from Quinnipiac University on Tuesday showed Mr. Cruz in a statistical tie for the lead with Mr. Trump in Iowa, raising the prospect that the billionaire developer might need to redirect his attacks toward a different challenger.

Mr. Trump has tagged Jeb Bush as “low energy” and made Senator Marco Rubio out to look like a lazy youngster, but what might he say about his friend Mr. Cruz? Here are a few possibilities:

Immigration: Mr. Trump has tried to make the case that he is the toughest candidate on immigration, insisting that anyone who entered the United States illegally must be deported and apply for legal status, and he could find some ways to paint Mr. Cruz as soft on the issue. Mr. Rubio has already offered some assistance in that area, noting this month that the Texas senator once backed a big increase in visas issued to bring foreign professionals with college degrees and special skills into the country. Mr. Cruz also proposed an amendment to the so-called Gang of Eight immigration bill that would have maintained a provision to give undocumented immigrants a way to gain legal status to remain in the country.

Campaign Finance: Mr. Trump has blasted his rivals as patrons of big donors, arguing that they can be bought and sold easily while he is independent because of his wealth. Although he has directed much of his criticism on this front at Mr. Bush, more than $30 million has poured into political action committees that support Mr. Cruz’s campaign, leaving him vulnerable to similar lines of attack.

Roots: Not shy about getting personal with his adversaries, Mr. Trump is famous for raising questions about Ben Carson’s religion and, as a leader of the “birther” movement, President Obama’s country of origin. He could use a similar tactic with Mr. Cruz, who was born in Canada to an American mother. While most scholars agree that makes him eligible to be president as a “natural born citizen,” some have raised questions about whether Mr. Cruz’s roots should disqualify him.

Although such material may be available, will Mr. Trump go there? Last week, in an interview on CNBC, he signaled that he would.

“If he catches on, I guess we’ll have to go to war,” Mr. Trump said.