If we're talking total strangers who have only ever heard of him...Alec puts a lot of work into laundering his reputation. The first thing people tend to hear about him is his involvement in the Underwood Foundation, a non-profit organization dedicated to increasing access to medical care both domestically and internationally, in addition to war/disaster relief and refugee resettlement efforts. Alec's name, face, and grubby little mitts are all over the Foundation, so it's heavily associated with him and goes a long way towards making sure people think of him as close to sainthood.

More personally, Alec is known as a social butterfly, always hosting some social event or another. He and his wife are also known as patrons of the arts, having an impressive private art collection and devoting resources towards the preservation of art, and they're also both invested in a number of business endeavors independently - in Alec's case, particularly the shadow corporation now known as the Downgate Conglomerate, a controlling interest of which has been in the family for generations.

These are things that complete strangers with no connection to Alec might know from reading about him in the newspaper. If you want to know what people closer to him, but not close, think of him, that's a separate question. Thank you for asking!