Senegal's opposition joined forces Sunday in a mass rally to block 85-year-old President Abdoulaye Wade from landing a third term in office and back challenger Macky Sall. The 12 presidential candidates who fell out of the running in a first round of voting on 26 February have formed a coalition they hope will usher ex-prime minister Sall into power. Wade is facing a stiff battle to retain power at the March 25 poll after a strong opposition showing crushed his hopes of overall victory in the first round and forced him into a run-off.