Im doing the Arizona Killer quest and keep getting recognized every time I. Does anyone have a suggestion on how I can finish the quest.

Kill 'em all, what's the problem?

Stay away from Rangers, use stealth-boys and when all else fails always listen to the Finn

Wear Ranger Armour, and keep away from Rangers.

Or, plant a bomb on the Vertibird and make your presence known.

Walk to Hoover dam and walk to the left of the statues and away from rangers and walk up to your guy and say your ready and just stand still in the crowd

Cheers

Before the quest even begins, lay mines on the President's stage & hack Bear Force One's flight control terminal. Then sneak around and lay mines along the path back to the Vertibird after the President arrives.

This way, you can stay in hiding and Kimball either gets both a harrowing escape to the helicopter and then dies anyway. True mastery of the situation.

-Nukeknockout

Wear NCR armour and put C4 is the Privates hat then make it go BOOM when he is beside Kimball !!!
Or kill them all, thats what I did.

Wearing NCR armor only helps a little, as you're still marked a terrorist by this point and all of the various Rangers stationed there can see right through the NCR disguise. A Stealth Boy was the only way I could handle that situation without it turning into an instant gunfight.

I did it with only NCR Armour, and managed to get right amoung the front row of spectators, even managed to rig the AA gun with out getting spotted through the disguise.
Remain cruched [Hidden] for aslong as you can until Kimball arrives or take Cutter's advice and use a Stealth Boy.

As for the how of it, I snuck into the guard tower overlooking the stage, knifed the guard, and shot president Kimball once in the head with the silencer rifle right after he said "It is because of men and women like Private First Class Jeremy Watson that Nevada and the New California Republic remain free and secure." Real classy. Then I took out damn near all of them from that guard tower while the profilgates scrambled about. Ran outside and hacked the rest to death with the knife. Nobody knew what was happening.

I waited near the door he goes through after leaving his Vertibird, and just used my Spiked Knuckles.