WASHINGTON: Donald Trump is expected to launch his re-election campaign Tuesday (Jun 18), kicking off an age-old battle that most sitting US presidents wage for four more years of power.Recent history suggests that the 2020 advantage goes to Trump - although Democrats have fielded an extraordinarily diverse group of candidates pursuing the nomination, and the brash New York billionaire has been saddled with scandal and calls for his impeachment.Can Democrats overcome Trump's dominant position and reclaim the White House? Here is a look at how the power of incumbency impacts presidential politics.IS PAST PROLOGUE?Of America's 44 previous presidents, just 15 served two full consecutive terms. But recent elections have especially favored sitting presidents.Since World War II, only three incumbent candidates have failed to win re-election. The three presidents prior to Trump - Bill Clinton, George W Bush and Barack Obama - all won two terms.ADVANTAGESModern-day presidents are … [Read more...] about Incumbency is powerful. Is Trump poised for re-election?