changing jobs during a PR

My PR was started a couple of months ago. A staffing company is wanting me to do a 6 months for hire job. How does this work since mt PR is going on. I was told that the PR backlog is 500 days. So in my case once I left my current employer my PR would be canceled. The temp company would take the clearance. and what transfer it to the main company if hired? What is the downside to this. I was told awhile ago that I can not jump ship until the PR is completed. Is this true? Thanks

You are free to jump ship as you desire. If the current sponsoring company really wants you they will continue to sponsor you, even if you are not currently drawing a paycheck there. It is with the understanding you will accept a position should they get you cleared. If the temp job also has cleared functions they can sponsor the clearance as well, picking it up from the previous sponsor.