Yeltsin's main opponents and would-be successors, Moscow Mayor Yury Luzhkov and former Chairman of the Russian Government Yevgeny Primakov, were already campaigning to replace the ailing president, and they fought hard to prevent Putin's emergence as a potential successor. Putin's law-and-order image and his unrelenting approach to the renewed crisis in the North Caucasus, which started when the Islamic International Brigade based in Chechnya invaded a neighboring region starting the War in Dagestan, soon combined to raise Putin's popularity and allowed him to overtake all rivals.