We got this small tree from Arbor Day Foundation a couple of years ago. Poor thing had a really bad time in the heat plus drought we suffered here in NE TX last summer. We did water it and thus it survived - barely.
This year it leafed out but the shoots at the base seem far more 'healthy' than the top part. The question is, should we cut off the original trunk/stem and let the shoots grow? Or, should we cut off the shoots so the plants resources go to the original trunk/stem?
I think the A.D.F. sells grafted red Maple trees. If so, what the healthy looking stem is coming from is a root-stock tree, and you don't want that one - it won't be a red Maple. I am sure someone will come by and give you correct information, but this would be MY guess.
If this is indeed a grafted (named) Red Maple, it was most likely grafted onto seedling Red Maple understock - which is what the foliage in the image looks like to me. This IS Red Maple, but the understock won't have the characteristics of the named/grafted top.
I don't think the top looks THAT bad, but you need to be the judge. If you are able to coddle this plant through another growing season, then I'd prune off the sucker at the base and let the top have a go at it. If you just want a vigorous plant and don't care if this is a seedling or not, let the sucker fire away. I'd tie it off to the main stem there to get it growing vertical this year, and then cut off the old trunk right before next spring's growth.