Since President Obama took office, Americans have seen a rise of the right. The Tea Party has reinvigorated U.S. politics in general and the Republican base in particular.

The government, Democrats and Republicans, has shifted slightly to the right to accommodate the Tea Party.

A policy must be able to gain Tea Party support if it is to move forward. In order to avoid government default or shutdown, the Democrats have had to acquiesce. This has been to the chagrin of many Democratic voters, particularly those who had such high expectations for President Obama. Might we now see a rise of the left? I think so.

With more registered voters identifying themselves as Democrats than Republicans, it would seem intuitive that a rise of the left is not only likely, but rational. In 2008, registered Democrats had a 9 percent advantage over Republicans and most Independents leaned Democrat. With these numbers in their favor it would seem the Democratic base would have an easier time controlling the policy debate. But it has failed to do so.

Money is not the answer, as Democratic voters have relatively similar incomes to Republican voters. And there seems to be as many high-profile celebrities on the left as there are wealthy business people on the right. For every Koch brother there is a Bill Gates, Leonardo DiCaprio, or Barbra Streisand. In 2008, voters who made in excess of $200,000 a year were more likely to vote for Barack Obama.

One reason why Democrats do not have a permanent advantage is that Republicans are more politically engaged than Democrats. This means that even though they are the minority, they are a vocal minority whose collective voices are louder than those on the other side. The numbers show that since 1980, and with the exception of 2008, Republicans turn out for elections at a higher rate than Democrats. If the Democrats do not get the government they want, it is their own inability to organize and voice their concerns that is to blame.

The Republican Party has embraced a clear political ideology. The Democratic Party is supposed to be the party on the left, but it has not embraced a leftist ideology. Without a clear ideological connection the Democratic Party will not be able to energize its base on a regular basis.

Mass movements require an ideology to sustain themselves over long periods. Charismatic leaders and slogans will only take a movement so far if it lacks a set of core values that people believe in. Getting people engaged is hard enough, getting them to stay engaged is almost impossible.

The reason why we have not seen the Democrats embrace a leftist ideology, or have seen a left-wing party develop, is partly historical. Our country does not have a history of deep ideological cleavages. There has never been a viable socialist party in the U.S. Likewise there has never been a large disparity in power that has warranted a class uprising. England, France, Japan, and Germany all have parties that represent an ideologically motivated left. Our left is not ideologically motivated or distinctive.

We have not seen a rise of the left because leftist ideals are not popular among Democrats or Republicans. There are not many, if any, Democrats who would openly defend a socialist policy and identify it as such. But this could change. Voters on the left feel alienated by those they voted for, those who ran idealistic campaigns but have not run an idealistic government. And with the growing disparity in wealth, the time might be right for a rise of the left.

Those who are looking for a third party in the U.S. are looking in the wrong place. They predict the Tea Party could be it or that a candidate like Donald Trump may run as an outsider. This won’t happen.

To have a third party, a large, energized group needs to feel alienated and unrepresented. The Tea Party controls the House of Representatives and will decide the Republican presidential candidate. The Tea Party, to itsr credit, is getting its way as much as any single group can in our system.

Either because Democratic leaders are not ideologically aligned with the left or because they lack the political savvy to get their policies past the opposition, the interests of the left are not being represented. This means that if the left is to have its voice heard, those on the left must go somewhere other than the two dominant parties.

Kyle Scott teaches political science at Duke University. Scott has authored three books, most recently, "Federalism: A Normative Theory and its Practical Relevance" (Continuum; 2011).