The 44-year-old activist is well known nationally for his reports on the corruption that has flourished under President Vladimir Putin’s government. His wide support puts the Kremlin in a strategic bind — risking more protests and criticism from the West if it keeps him in custody but apparently unwilling to back down by letting him go free. Protests erupted in dozens of cities [90] across Russia on Saturday to demand the release of opposition leader Alexei Navalny, the Kremlin’s most prominent foe. Police arrested more than 3,000 people, some of whom took to the streets in temperatures as frigid as...