Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: (CNN) A pair of veteran leaders on the left, former Democratic National Committee Chairman Howard Dean and Center for American Progress President Neera Tanden, called on Hawaiians to vote Rep. Tulsi Gabbard out of office after the Democrat questioned whether Syrian President Bashar al-Assad was responsible for last week's chemical attack. "People of Hawaii's 2nd District -- was it not enough for you that your rep met with a murderous dictator? Will this move you?" Tanden tweeted Friday in response to Gabbard's comments on CNN that she is "skeptical" Assad is responsible for the chemical attack. Dean compared Gabbard's comments to President Donald Trump's Twitter blasts.'Why should we just blindly follow this escalation of a counterproductive regime-change war?' Gabbard askedA handful of mavericks in Congress have said they want to see more evidence of Assad's involvement 
 Question:Gabbard has also said she is concerned about sparking a nuclear war with Russia, which backs the _ regime.

Assad