National could still be tarnished by an ongoing saga around its donations

The Serious Fraud Office has filed criminal charges against four people in relation to donations paid into a National Party electorate bank account.

But leader Simon Bridges says it's neither him nor anyone in the party

Auckland University political marketing and communication researcher Dr Edward Elder says that might not be enough.

He says because we don't know how closely aligned with the National Party the four people charged are, it could still be seen as a National Party problem.