switch contact ratings

[SPK627]

I have a switch that is rated for 125VAC, 0.3 A. My question is if I use it in a 70VAC, 35W circuit, producing a current of 0.5A, am I trouble?

 

[buzzp]

Yes, the current ratings and voltage ratings BOTH need to be accounted for when switching. The current rating needs to be 0.3A or less and the AC voltage switched, needs to be 125VAC or less.
The voltage is important to prevent arcing between contacts and insulation strength. The current is important to prevent over heating of the contacts (welding together).
Your switch will not work in this application.