Ted Cruz's Surge in Iowa Has Donald Trump Playing Defense

— -- Since Donald Trump and his helicopter descended on the Iowa State Fair back in August, the billionaire businessman has been the steady front-runner in Iowa, surviving attacks from fellow candidates, controversial proposals and a short-lived burst in two polls from Dr. Ben Carson.

Now, seven weeks away from the Iowa caucus, Trump is fending off his biggest threat yet from Texas Sen. Ted Cruz, the co-front-runner in the state after four polls released in the past week show his surge.

“I think Cruz is the front-runner in Iowa and the reason is he’s always been a natural fit of the caucus-goers," Iowa Republican strategist Craig Robinson told ABC News. "He's a true conservative and doesn’t have a lot of competition within his own lane. There's Rick Santorum and Mike Huckabee, but they're not even on the main debate stage and I think that matters to voters."

Robinson believes winning Iowa remains complicated for the Trump campaign because they're counting on bringing a new group of voters into the party. "Cruz is appealing to the people who caucus all the time. He has an easier lift," Robinson says.

The biggest lead for Cruz comes courtesy of the Des Moines Register-Bloomberg Politics poll released Saturday, which shows Cruz up 10 points over Trump among likely Republican caucus-goers, jumping 21 percent since the last DMR/Bloomberg poll conducted two months ago.

Cruz also led the field in the Monmouth University Poll released last Monday and a Fox News poll that came out Sunday with 28 percent, followed by Trump's 26 percent, although Cruz's lead is within the poll's margin of error.

But two other polls show just how close the race in Iowa is. A Quinnipiac University poll released Monday has Trump ahead at 28 percent and Cruz right behind him at 27 percent -- both with twice the support of Marco Rubio who is in third place with 14 percent. Also, Donald Trump is not allowing anyone to forget a CNN/ORC poll released last week where he holds a commanding lead in the Hawkeye state, 13 points ahead of Cruz.

Ann Selzer, who has polled for the Des Moines Register for decades, told ABC's This Week Sunday that, “while we have seen roller coaster rides in other caucuses, we’ve never seen a spike like this for a candidate," referring to Cruz's jump. The Senator's lead is also accompanied by the highest favorability rating in the GOP field at 73 percent.

Cruz has been gaining momentum in Iowa over the past month, seeing larger numbers at his events and increased fundraising. He has also received some key endorsements from the Evangelical Christian community, who make up roughly 42 percent of Republican voters in Iowa.

"I always expected that Cruz would do well in Iowa. Either win or finish in the top three," says Richard Schwarm, the former chairman of the Iowa Republican Party. "The Trump phenomenon took us all by surprise, but the Cruz phenomenon has not. I don't think he’s peaking too early."

Trump, 69, doesn't seem to believe Cruz is peaking too early either, as he went after Cruz's Cuban roots Friday night at a Des Moines town hall where he told his supporters Iowa is a "two person race."

"Not a lot of Evangelicals come out of Cuba, in all fairness," Trump said in an apparent shot at Cruz's heritage.

Trump also took aim at Cruz's ties to big oil and his refusal to back ethanol subsidies, an important issue to Iowa voters, as ethanol production is responsible for thousands of jobs in the state.

"Everything I say, he agrees with me, but with the ethanol he’s got to come a long way cause right now he's for the oil....I say to myself, if Ted Cruz is against ethanol, how is he winning in Iowa?" asked Trump.

When Carson took the lead in two late-October Iowa Polls, Trump showed anger toward Iowans, even acting out a story from Carson's childhood, asking the crowd at a Ford Dodge, Iowa, rally, "How stupid are the people of Iowa to believe this crap?"

But with Cruz, 44, Trump is so far staying close to the issues, although he did call Cruz "a maniac" for his temperament in the Senate while on Fox News Sunday. Cruz replied with this tweet:

There's no doubting how badly Trump wants to win Iowa, telling his supporters Friday night that he thinks he could "run the table" after an Iowa victory.

"Iowa has been amazing,” Trump said. “We’re doing so well. I’m going to be here a lot in January. You’re going to be so sick of me. You’re probably going to say, ‘I can’t stand the guy.’”