No lady is ever, except to the President of the United States, a cardinal, or a reigning sovereign, presented to a man. The correct introduction of either a man or woman:
To the President,
is,
"Mr. President, I have the honor to present Mrs. Jones, of Chicago."
To a Cardinal,
is,
"Your Eminence, may I present Mrs. Jones?"
To a King:
Much formality of presenting names on lists is gone through beforehand; at the actual presentation an "accepted" name is repeated from functionary to equerry and nothing is said to the King or Queen except: "Mrs. Jones."
But a Foreign Ambassador is presented, "Mr. Ambassador, may I present you to Mrs. Jones."