Tottenham completely dominated the match and Kane put them ahead with a cool first-half finish moments after Alli had struck crossbar.
Watford’s afternoon got worse when Alli struck for his second and Spurs’ fourth just 58 seconds into the second half after further poor defending from the hosts.
Water Mazzarri’s side pulled one back in the 92nd minute when Kaboul bundled over the line after initially being denied by Hugo Lloris, but they drop to 13th having taken just four points from their last seven matches.
Tottenham move back to within 10 points of leaders Chelsea, who they meet in a crunch clash at White Hart Lane on Wednesday.
Son Heung-min – in as one of four Tottenham changes – forced Heurelho Gomes into an early save, before fast-starting Spurs had a penalty claim turned down.
It was still all Tottenham when Alli collected Son’s pass and fired a blistering strike against the bar from 25 yards, before the deadlock was deservedly broken in the 27th minute.
Trippier sent an acute pass from the right into Kane’s path and he beat Gomes at the near post to mark his 100th top-flight appearance in style.
That duo combined to impressive effect six minutes later as Spurs made it two. After Alli found Trippier in space, he whipped in an outstanding cross which Kane converted from inside the six-yard box.
It should have been three when Son missed the target after Eriksen’s free-kick had given him an excellent chance, but Spurs were not to be denied.
Kane’s cross was dealt with awfully by Kaboul, allowing Alli to produce a composed finish into the far corner.
Another poor Watford clearance, this time from Sebastian Prodl, allowed Spurs to strike again after the restart.
The defender’s miscue gave Kane the chance to cross and Alli took one touch before converting from close-range for his fifth goal in three league outings.
A sharp save from Gomes kept out Kane’s free-kick as he searched for a hat-trick, with Watford struggling to make an impact at the other end.
Pochettino brought off Alli, Rose and Kane with the match against Chelsea in mind, Spurs coasting to victory with Lloris untroubled until Watford’s stoppage-time consolation when Kaboul converted Adlene Guedioura’s free-kick at the second attempt.
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