Is a FINRA-regulated funding portal necessary to do a crowdfunding raise?

The short answer is: yes, Regulation Crowdfunding requires that an issuer uses a crowdfunding intermediary.

I'm assuming when you say "crowdfunding raise" that you're referral to using Regulation Crowdfunding (Reg CF). Reg CF legally requires the use of a crowdfunding intermediary, which can be either a funding portal, or a registered broker-dealer. 

There are other types of securities-based "crowdfunding" - e.g. if you're looking to do a larger Reg A+ raise, then you are not required to use a crowdfunding intermediary - some issuers will do these campaigns on their own website. However, Reg A+ campaigns have much higher costs to launch due to more stringent disclosures and other legal and financial requirements.