HOUSTON, Texas: Vice President Kamala Harris took her presidential campaign blitz to the largest US teachers’ union on Thursday, promising a “fight for the future” as new opinion polls showed her narrowing the gap with Republican rival Donald Trump. Harris’ swift emergence as the successor to President Joe Biden, 81, as the Democratic presidential candidate in the Nov. 5 election has shaken up a stagnant presidential race, with polls showing her narrowing former President Trump’s advantage.