Yes, America has indeed become an oligarchy, by badly mixing democracy and oligarchy! Hear me out …
One of the biggest educational benefits for American voters 
throughout the 2016 Presidential election so far has, hopefully, been an
 improved understanding of how oligarchic, and rigged, our political 
system has become.

Simply put, it is heavily in favor of establishment candidates, and 
specifically against outsiders, with some party elites having profound 
influence over the outcome of an election, sometimes decisively!
1. What is an oligarchy?
Here is an excerpt from 
Wikipedia - Oligarchy:
Oligarchy (from Greek ὀλιγαρχία (oligarkhía); from ὀλίγος (olígos), meaning "few", and ἄρχω (arkho), meaning "to rule or to command")[1][2][3] is a form of power structure in which power
 effectively rests with a small number of people. These people might be 
distinguished by royalty, wealth, family ties, education, corporate, 
religious or military control. Such states are often controlled by a few
 prominent families who typically pass their influence from one 
generation to the next, but inheritance is not a necessary condition for the application of this term.
Throughout history, oligarchies have often been tyrannical, relying on public obedience or oppression to exist. Aristotle pioneered the use of the term as a synonym for rule by the rich,[4] for which another term commonly used today is plutocracy.
2. Who are the oligarchs in America?
Some elected officials and some elites in the political parties! Many
 candidates are chosen by the oligarchs, and become oligarchs themselves
 over time. It's the elites choosing the future elites who will dictate 
how we, the people, will be allowed to vote and live! THE BUSH's THE CLINTONS, THE OBAMA'S AND THEIR SYCOPHANTS. IT LIKE THE MOB FAMILIES !!
3. Oligarch vs. democracy
In a nutshell, democracy simply means 
one person, one vote. Americans naively believed they had finally achieved this ideal in 1965 (
Voting Rights Act of 1965).
Unlike a parliamentary system (e.g. the U.K., Japan, and Canada), in 
which the majority party of the parliament (via a coalition if 
necessary) elects the head of the government, Americans elect their 
President directly via a democratic process (with the electoral-college 
system notwithstanding), as clearly defined in the U.S. Constitution.
It turns out that American voters no longer really elect the 
President directly, at all. Instead, the two major parties each offer 
their choice of candidate, selectively chosen via their own primary 
processes. Worse yet, neither of the primary processes are truly 
democratic. Rather, they are oligarchic, with some party elites having 
profound influence over the outcome, sometimes decisively. Worst of all,
 there is no direct relationship between the primary voters and the 
party elites, because many primary elections are open, with no party 
affiliation required!
In short, the election process for American President is not truly 
democratic. Rather, it is a bad mixture of democracy and oligarchy!
4. America's 2-party system
Like 
Yin and Yang,
 it was natural for America to end up with two major political parties, 
currently the Democratic Party and the Republican Party.
Both parties are private, like elite private clubs, with their own 
rules, hierarchies, and steep entrance dues to become elites. For 
example, Senator Ted Cruz, just like Senator Obama, promised heavy 
future favors for support of his presidential run. American taxpayers 
would have to pay hugely to cover his campaign promises, just as we did 
after Senator Obama won the Presidency. Both of them are obviously top 
elites in their respective parties!
However, unlike private clubs with exclusive memberships, both 
parties are “open”, with arbitrary party memberships. For example, an 
Independent (who belongs to neither party) may choose to participate in 
the Democratic primary (in states with open primaries), but eventually 
vote for the Republican nominee in the general election. He (or she) may
 never have voted for either party before, thus having nothing to do, 
previously, with the elites of either party.
In short, democratically speaking, the oligarchs in America are not 
legitimate, because of the disconnection between them and the voters!
5. How do the two parties choose their respective Presidential nominee?
Each party has its own primary elections, which vary from state to 
state, to select a party nominee. Basically, a nominee is selected by 
the delegates, who are not necessarily directly chosen, even 
proportionately, by the voters.
On the Republican side, the problem is less obvious this year, 
because Donald Trump is already the presumptive nominee, thanks to an 
overwhelmingly large number of votes he has received.
In contrast, the Democratic Party may have a big problem coming up, 
if Bernie Sanders ends up with more "pledged delegates" via public 
voting than Hillary Clinton, who obviously has far more super-delegates 
to eventually out-number him!
What, then, is a super-delegate?
Here is an excerpt from 
Wikipedia - Super-delegate:
In American politics, a "super-delegate" is a delegate to the Democratic National Convention who is seated automatically and chooses for whom they want to vote. These Democratic Party
 super-delegates include distinguished party leaders, and elected 
officials, including all Democratic members of the House and Senate and 
sitting Democratic governors.
Note: Many voted for Bernie Sanders in the primaries
 for the person, not the party! Some of them may have never voted 
before, let alone voted Democrat. So they had zero input as to who would
 become a super-delegate, who could not therefore possibly represent 
them in any way!
Bottom line: How could our political system have 
devolved to the point that some party elites end up with so much more 
power than the people, deviating from the ideal of "one person, one 
vote"?
"They know what's better for the party" is obviously the pretended 
logic behind the set-up. In reality, however, it's just another power 
grab by the elite few: the oligarchs!
6. Do they know better, really?
Yes, they do, as most of them are career politicians!
What, then, is the problem? Most of them work primarily for their own benefit (aka "getting re-elected 
ad nauseam"), with their party a distant second, their constituents a remote third, and their country dead last!
To know what a typical Congressman like 
David Jolly does on daily basis, read: 
Republican congressman exposes one of Congress' dirty little secrets on '60 Minutes'. Here is an excerpt:
Jolly said, as a member of Congress, entire schedules work around
 making time to fundraise, in his case $18,000 per day, for their 
reelection campaign.
"Republicans, Democrats and Independents can all agree on one 
thing - the public did not elect Members of Congress to go to Washington
 and spend their time raising money for their re-election," Jolly said. 
"They are not paying members $174,000 a year to spend, in some cases 20 
or 30 hours a week, on the phone dialing for dollars. But that is 
exactly what is happening."
Bottom line: In politics, money is not everything; money is the only thing!
7. What's the end result?
Because of the link between money and elections/re-elections, the two
 parties often end up with similar candidates, especially in terms of 
ferocious spending and the resultant requisite taxation and borrowing! 
Specifically,
- The Democrats tax-borrow-&-spend for entitlements. For more, read: Democratic Socialism.
 
- The Republicans tax-borrow-&-spend for wars, for more, read: Democratic Imperialism.
 
Still wondering why our national debt already exceeds $19 trillion, and continues to rise rapidly?
Wonder not! It's the political system, stupid!
8. Discussion
Both parties are oligarchic, but the Democratic Party seems much 
worse. For more on the history of “super-delegates” and its implications
 this year, read: 
No, Sanders doesn’t stand much chance.
Now, why the Democratic Party is more oligarchic than the Republican 
Party? Maybe it has something to do with the nature of the Democratic 
Party? Three informative readings:
- The Democratic Party is the Party of New Slavery!
 
- Stupid Voters.
 
- Stupid Media.
 
For those “intelligent” Sanders voters, if you feel disenfranchised 
by his party, it’s time to board the Trump train for one main reason, at
 least: Trump is the candidate best at addressing your critical issues, 
such as fair trade and anti-war!
More profoundly, electing Donald Trump may be a unique opportunity 
for us to break the cycle of money and politics by both parties!
Yes, Trump, a 
de facto Libertarian (
Who is Donald Trump, Anyway?),
 has already hijacked the Republican Party, by beating all its 
establishment candidates! He will hopefully unite, reform, and expand 
the GOP in the coming weeks and months, leading to a victory in 
November.
On the Democratic side, Sanders is unlikely to beat the Democratic 
establishment. So Hillary Clinton will certainly be the nominee, thanks 
to the super-delegates!
Between Donald Trump and Hillary Clinton in the general election, here is a basic question for all Americans: 
America: Are We Still A Republic?
9. Closing
Give Donald Trump a chance to "make America great again", which may 
include changes to campaign financing and even the oligarchic system!