Yes. Pick the connect relation, pick the middle of the vertical line, then pick anywhere along the horizontal line.
And, for the endpoint selection make sure your intellisketch settings include endpoints:
Let me also give an "expert tip" to remember the MICE keys. When you are placing or modifying objects you can hit the keys on the keyboard to get that keypoint M=Midpoint E = Endpoint, you get the idea.
So when placing a line and you want to connect to the midpoint of another line, just hover over it and hit the M key --> Voila!
This works with the connect constraint as well. Choose the connect command. Hover over line one and hit M. Hover over line 2 and hit E and.....