There are always bits of jobs we don't like, but project managers typically work on the projects that they are assigned. It's fine to have preferences, but you're looking for someone who can respond to business needs even if that isn't their top choice of project.
Managing up means working well with people more senior than you. Project managers do this all the time, so it's good to find out how they make those relationships work.
Marketing is changing constantly at a rapid pace -- so anyone in a marketing role needs to know how to stay on top of and adapt to these changes. Do they know where to look for industry news? Are they familiar with and subscribed to top marketing blogs? What do they do when they see a change has taken place, like when Google updates their algorithm?
This gives you an indication of how they do their job. Someone who spends all day at the PC may suit your environment, or you might be looking for a project manager who gets out and visits clients most days of the week. Remember that they might be prepared to do something other than what they do now, so if you hear something that doesn't fit with the post you are recruiting for, don't rule them out before exploring this further.
It will show you what's important to them at work: green credentials, career progression, work/life balance, working for a big brand etc. It will also tell you if they are actively job hunting or whether they saw your ad and couldn't resist (either is fine).
Before giving you an answer, the best candidates will come back and ask you about the blog's metrics, how many leads and customers it generates, what the goals are for it, how much you're investing in it, and so on. This is also a great way to test whether they actually prepared for the interview by reading your blog.
This will help you work out if they are happy to be honest and tell you about a time that something went wrong. This shows their capacity to learn from mistakes and how they deal with information overload. Delegating work packages is key to project work and you'll want to hire someone who understands that.
Not everyone has the chance to work on business critical, exciting projects that make for a great CV, but everyone has the chance to offer some suggestions for improvements (even if they aren't taken up). Look for someone who has ideas and who isn't afraid to put them forward.
It will show you their priorities and whether they have actually thought about what a project manager does. It will also demonstrate whether they are a good cultural fit for your team. If you have a strong focus on process and they think the most important thing is to be flexible and adapt processes as you go, then you probably won't get on.
If candidate's answer on above question is $0, they are lying. If they are unsure and say not that much. They are lying. If they are truthful and say quite a bit, and then go on to explain how that taught them lessons on strategy development, budgeting etc, then I'd hire them.