If Romney tries to primary POTUS for WH in 2020, she should step down. There would be no way she could credibly claim any sort of neutrality here, regardless of what she's saying right now.
https://www.breitbart.com/politics/2019/01/02/rncs-ronna-mcdaniel-calls-uncle-romneys-anti-trump-op-ed-disappointing-unproductive/