need to start talking to the Houthis. And if the Americans are talking to Iran in back channels, they need to do the same with the Houthis. Since Hadi's resignation, there has been a lot of anger against the Houthis in parts of the country, said Al Rowas, the IHS Country Risk analyst. While Hadi was n't able to unify the country while in power, she said, since the Houthi takeover of Sanaa, he has become the popular symbol of anti-Houthi sentiment across southern and central Yemen. Many there are calling for his return, she said. A chief flashpoint for popular anger may be the central Marib province, she said. There have already been some low-level confrontations, and tribes are mobilizing in the area. Large-scale protests have also been seen in Aden, the main seaport in the country's south, where the current chaos plays into the hands of the secession movement. 7 things to know about Yemen CNN's Tim Lister, Nick Paton Walsh and Jomana Karadsheh contributed to this report.