Entering the New Vegas Strip for the first time, you'll be greeted by Victor one last time. He will tell you that his boss (Mr. House) wishes to speak with you in the Lucky 38.
Detailed walkthrough
The first time you try to enter New Vegas Strip, you'll be halted by some securitrons. Find a way past them and immediately after entering The Strip Victor will be rolling your way again.
After some pleasantries, he insists you visit the Lucky 38 Casino and meet its owner, Mr. House, who's been asking for you to come by.
Whether you accept Victor's offer or not, the main quest The House Always Wins begins.
Notes
After the conversation Victor will stay in the Lucky 38 or outside it.
It appears to be 2 different Securitrons that switch to Victor once inside and outside the Lucky 38. Similar to the Securitron outside Victor's shack.
It is possible to talk to the Victor right in front of the door to the Lucky 38 before talking to Victor on the street. The Victor on the street will talk to you directly after, which can even be confusing to some players who have played through the game several times.
Bugs
PC If the player leaves right after passing the credit check, the quest will never occur.