What does "The deck is stacked" in Hillary Clinton’s presidencial candidacy announcement mssage mean?

Washington Post’s (April 15) carries an article under the title, “Hillary Clinton sounded a little like Elizabeth Warren in 2008, too” accompanied with the following lead copy.

“Hillary Clinton's announcement video Sunday included a clear-as-day shout-out to Elizabeth Warren. "The deck is stacked" against average Americans, Clinton argued, echoing Warren's "System is rigged" mantra.” From The Washington Post.

AP Radio News (April 13) also reported that:

"The former First lady, Senator and Secretary of State jumped into the race in an online video. She wants to be the champion of average American, adding "the deck is still stacked in favor of those of the top."

What does "The deck is stacked (against average Americans / in favor of those of the top)” mean? Could you paraphrase it in plain words?

As I understand it in normal card game it would mean someone manually prepared the cards so they know what is coming (have advantage)

In the context of the speech I think it means that average Americans are at disadvantage.

Similar to system is rigged in your post.

stack the deck (against someone or something) and stack the cards (against someone or something)

- to arrange things against someone or something; to arrange things secretly for a desired outcome. (From card playing where a cheater may arrange the order of the cards - stack the deck - that are to be dealt to the players.) - I can't get ahead at my office. Someone has stacked the cards against me. Do you really think that someone has stacked the deck? Isn't it just fate? - TFD idioms