GOP state senator Joni Ernst and Democratic Representative Bruce Braley held their first debate last night and both sides went on the attack.

On immigration, the battle lines were clearly drawn:

Mr. Braley, a Democrat, said that Congress has missed an opportunity to fix what he called the nation’s broken immigration system, because House Speaker John A. Boehner, Ohio Republican, has refused to take up a bill that passed the Senate with the support of Republican Sens. John McCain of Arizona and Marco Rubio of Florida.

“Will you join John McCain and Marco Rubio in calling on Speaker Boehner to bring this immigration bill to the floor of the House so we can pass it?” Mr. Braley asked Mrs. Ernst.

Mrs. Ernst, a Republican, said that Congress should “secure the border,” “enforce the laws on the books” and then move to “modernize” the legal immigration system.

She said, “I don’t support amnesty” and said she is opposed to President Obama taking executive action to “grant amnesty” — which some conservatives fear he will do after the 2014 mid-term elections.

“I do support bringing a lot of these illegal immigrants forward, but not granting them amnesty,” she said. “We have 5 million people waiting in line right now to receive U.S. citizenship and we need to honor that commitment to those people.”

Mr. Braley shot back that “Sen. Rubio and Sen. McCain did not vote for amnesty” by supporting the Senate immigration bill, which would grant quick legal status to most illegal immigrants and create a new specific pathway that would let most illegal immigrants get citizenship in about 13 years.

“Amnesty is when you break the law and there are no consequences,” Mr. Braley said. “That’s why they voted for this bill. It has real serious tough consequences including an admission that you broke the law.”

Bringing John McCain into the debate on immigration may have not have been the best strategy in Iowa - or anywhere. Nor is Marco Rubio very popular in the Hawkeye State. Braley can argue that the Senate bill does not grant amnesty to illegals all he wants to, but that's the perception that's out there. He would have been far better off keeping his mouth shut about amnesty and highlighting other aspects of the bill.

Meanwhile, Ernst took dead aim at Braley's contention that he's bi-partisan:

Mr. Braley called himself a “bridge builder,” not a “bridge burner.”

Ms. Ernst ridiculed the idea that Mr. Braley was bipartisan, bringing up a feud that erupted with his neighbor earlier this year over chickens.

“Congressman, you threatened to sue a neighbor over chickens that came onto their property,” she said. “You’re talking about bipartisanship, how do we expect as Iowans to believe that you will work across the aisle when you can’t walk across your yard?”

Score one for Ernst.

The danger is that Ernst will sit on that 6 point lead she's got rather than keep attacking and go  for the jugular. The Dems aren't finished pouring money and resources into Iowa and the GOP better be ready to counter that effort with a maximum fundraising drive of their own.