How do I eliminate political iPhone text message spam?

Apple is going to display every message that is sent to your phone unless that number is able to be specifically blocked. That is exactly what the phone is supposed to do and anything beyond that is out of Apples control. Here are several options for you:

• Your cell provider may have a Spam Blocker option that you can use to prevent the message from being sent to your iPhone.
• You can verify you are on the Do Not Call registry
• You can contact your politician to lobby against these intrusions, but may just get lip service since that is how they raise funds.
• Review the rules on Political Robotexts and report to the FTC.

https://www.fcc.gov/rules-political-campaign-calls-and-texts

• Review recent RoboCall news and legislation for more information on reporting and which legislators to support.

https://www.fcc.gov/consumers/guides/stop-unwanted-robocalls-and-texts

Perhaps some pro-active stance might help relieve your

iPhone the burden of these various text of questionable

origins and unwanted to most who get them?

When you can, report each of those as phishing, spam

or some actionable field of identifier; so they go away.

Block, filter, and report messages on iPhone - Apple Support

Additional ideas may appear by substitution of words

in Search. re: replace Phishing with Spam; and so on.

https://duckduckgo.com/?t=ftsa&q=phishing+text+iphone+stop&ia=web

Some ideas that I've used with older iPhones do OK

and appear; along with others that were not as good.

..And items that might do OK with macOS, seem not

do as well, where an iOS device is used. This varies.

Also try to not text or leave cell number with those

who may see that as an open door to abusive acts.

Someone in another thread recommended an app called, I believe, Sifter, that they said was annoying to set up but, once they got it set up, it screened out the political texts.