It's interesting to see which song was at #1 at the moment the mentioned song reached #2, as Hello Goodbye is doing.
These were the #1 hits of my previous #2 mentions:
"She's Not There" (The Zombies) was second to "Mr. Lonely" (Bobby Vinton) in December 1964.
"Barbara Ann" (The Beach Boys) was second to "We Can Work It Out" (The Beatles) in January 1966.
"Daydream" (The Lovin' Spoonful) was second to "(You're My) Soul And Inspiration" (The Righteous Brothers) in April 1966.
"Never My Love" (The Association) was second to "The Letter" (The Box Tops) in October 1967.
"Born To Be Wild" (Steppenwolf) was second to "People Got To Be Free" (The Rascals) in August 1968.
"Proud Mary" (Creedence Clearwater Revival) was second to "Everyday People" (Sly & The Family Stone) in March 1969.
In a couple of cases I'm not familiar with the #1 hit!