Wheeler-Dealer

Connoting scam or substandard salesmanship?

Maybe both.

wheel and deal
Operate or manipulate for one's own interest, especially in an aggressive or unscrupulous way. For example, Bernie's wheeling and dealing has made him rich but not very popular. This term comes from gambling in the American West, where a wheeler-dealer was a heavy bettor on the roulette wheel and at cards. [Colloquial; c. 1940]
The American Heritage Dictionary of Idioms by Christine Ammer © 1997 by The Christine Ammer 1992 Trust