Not sure what a typical eCPM for a news / political blog is, but in casual mobile gaming, you typically expect between $1 and $5 for every 1K interstitial ad impressions (the annoying ones that pop-up uninvited). That would translate to around $500-$2,500 a month for 500K ad impressions. But that is also for a super relevant audience. I.e. other mobile gaming companies are advertising their games to your users, who are obviously people already interested in playing games.

For a news / political blog, I imagine the eCPMs would be lower as the audience is more varied, and hence less valuable to any particular advertiser. Your figures may actually be quite typical. You may need to consider adding some alternative monetization strategies. Affiliate marketing might be one. Adding a premium subscription option with premium content/ads removed/some other feature could be another.