after trailing in the polls
... that U.S. President Harry Truman won an upset victory in 1948 after trailing in the polls by a significant margin throughout nearly all of 1948?
... that <a class="mw-redirect" href="./U.S._President" id="mwAZk" rel="mw:WikiLink" title="U.S. President">U.S. President</a> <a class="mw-redirect" href="./Harry_Truman" id="mwAZo" rel="mw:WikiLink" title="Harry Truman">Harry Truman</a> won an <a href="./Upset_(competition)" id="mwAZs" rel="mw:WikiLink" title="Upset (competition)">upset victory</a> in 1948 <b id="mwAZw"><a class="mw-redirect" href="./Historical_polling_for_U.S._Presidential_elections" id="mwAZ0" rel="mw:WikiLink" title="Historical polling for U.S. Presidential elections">after trailing in the polls</a></b> by a significant margin throughout nearly all of 1948?