Picking up where they left off, U.S. Sen. Jeanne Shaheen and her Republican challenger Scott Brown on Thursday used their latest debate to again emphasize their differences on immigration, the Islamic State group, Ebola and their efforts to help small businesses.

Shaheen, a Democrat and former governor, is seeking a second term in the U.S. Senate. Brown moved to New Hampshire last year after losing the seat he had won in 2010 to replace the late Sen. Ted Kennedy in Massachusetts. Polls show a tight contest, and the race is among those expected to determine control of the Senate.

In their third debate this month and second one this week, Brown criticized Shaheen on Thursday for not joining him in backing a ban on travel to and from the West African countries ravaged by the Ebola virus, calling it the latest example of her blind devotion to President Barack Obama.

"It's very typical that Senator Shaheen waits to get the OK from the president to do many different types of things," Brown said.

Shaheen said she'd support a ban if experts determine it would work, but that Brown is fear-mongering by trying to tie the issue to the need for greater U.S. border security.

"We don't need people who don't have medical expertise trying to get people concerned about what we've got to do to respond," she said.

Brown, who has made border security a key issue in his campaign, bristled when Shaheen later criticized him for not backing a comprehensive border security and immigration reform bill and for missing Homeland Security Committee hearings in the Senate. Noting his long career in the National Guard, he said he doesn't need anyone to tell him how porous the border is.

"There is a rational fear from citizens in New Hampshire and throughout this country that people are coming — criminal elements, terrorists, people with diseases coming through our border. So with respect, I don't need to attend those hearings," he said.

Brown in turn criticized Shaheen for missing Foreign Relations Committee hearings, including one about the rising threat of the Islamic State group. He argued that Obama's decision, backed by Shaheen, to not leave a transitional force in Iraq allowed the militant group to flourish, and repeated his claim that the group "wants to plant a flag at the White House." Shaheen said Brown was being irresponsible in "repeating ISIS talking points."

The two also tangled over their support for the state's small businesses, with Brown touting his endorsement by several national business groups, one of which gave Shaheen a "zero" rating. Shaheen listed several bills Brown voted against that she said helped New Hampshire companies, and said he voted to give tax incentives to companies that ship jobs overseas.

"We don't need to import a candidate who's going to outsource our jobs," she said, repeating one of her applause lines from a Democratic Party fundraiser last week.

Brown countered that small businesses are being hurt by the health care overhaul law Shaheen supports. He wants to repeal the law and argues that states could develop their own plans to make health care more affordable and accessible. Shaheen said Brown wants to force thousands of people to lose coverage and return to a time when insurance companies could deny coverage based on pre-existing conditions.