cheltzel

It looks like you are arriving at 16:00 on UA959 and connecting to the last UA flight to TPA which departs at 18:01

I looked up UA959's on time history on FR24 and over the last 90 days it has only been seriously late twice. On Jun 21 it arrived at 18:25 and on April 1 it arrived at 17:09. If you get a similar delay, you will likely be spending the night at ORD. The good news is a significant number of UA959 arrivals are much earlier than the scheduled time of 16:00. Often earlier than 15:30.

So you should be prepared for what you need to do if something happens and your LHR flight is seriously delayed but the odds are significantly in your favor for making your TPA flight.