The Flight Crew of a CRJ-700 ordered the aircraft evacuated just prior to takeoff due to visible and pungent smoke and fumes in the cockpit and cabin.

Narrative

Just prior to being cleared onto the runway for takeoff; the Captain and I agreed that we smelled smoke. At this time I also noticed smoke coming out one of the vents nearest to the Captain. I quickly called back to the flight attendants to see if they also smelled smoke. They did and I told them to evacuate the aircraft. We then ran the QRH evacuation checklist and; in doing so; advised ATC that we were evacuating the aircraft. After finishing the evacuation QRH; I exited the airplane through the main cabin doors and started organizing passengers in a circle away from the airplane in a safe location. The overwing emergency exits were used as the passengers deplaned as well. There were three minor injuries during the evacuation. All 70 passengers and four crew exited the plane in a very timely but controlled manner.We had the aircraft all morning and had not experienced anything out of the ordinary prior to this incident. We were holding short of the runway with the before takeoff checklist complete down to the line; the APU off and bleed air coming from the engines. The smoke came on very quickly and was visible. It had an overpowering smell of sulfur.