たばこは体に悪いとわかってはいるものの、なかなかやめられない。
If it's は, does omitting は change the meaning in verb-te~はいる? And also, could you talk about what いる is doing?
If it's はいる, in what sense would you describe はいる's usage?
Also, as I googled for more examples, I noticed there was a general pattern of てはいる[が・けど・ものの]、... Is there something to this?