There are less than 24 hours to go before the Iowa caucuses.

At this point, even without the first votes of the 2012 GOP presidential primary yet to be cast, here is what I can say without equivocation about this political year.

For starters, this is the most unsettled presidential field I have seen in over 30 years of covering politics. The last six months have brought us a rapid succession of political boomlets from candidates not named Mitt Romney. And right now 41 percent of people likely to attend an Iowa Caucus tell the Des Moines Register that they still “could be persuaded” to change their minds.

That signals strong, persistent Republican voter discontent with this field of candidates.

Let’s name the shooting stars we’ve seen catch fire and then fade among Republicans this season – beginning with Donald Trump, Michele Bachmann, Rick Perry, Herman Cain, Newt Gingrich, and Ron Paul. They have all enjoyed stints as the GOP frontrunner. They have all, at one point, topped the national polls and garnered a plethora of media attention, only to watch their leads disappear as quickly as they emerged.

Now the latest shooting star is Rick Santorum. According to the Des Moines Register’s most recent Iowa poll of likely caucus-goers, Mitt Romney narrowly leads the field with 24% support, Ron Paul is in second with 22%, Santorum has surged to third place with 15%, Newt Gingrich is in 4th with 12 percent and Rick Perry is in fifth place with 11% support. Michele Bachmann is last.

The fact that the field is so unsettled with just days remaining indicates that there is something deeper going on in the Republican Party. What accounts for the unwillingness of the GOP electorate to coalesce around one candidate?

I believe the answer to that question lies with the Tea Party movement.

It was one year ago that that the Tea Party wave helped Republicans retake the majority in the House of Representatives and increase their numbers in the Senate. That year, the GOP also won governorships and captured state legislatures across the country.

As good a year as it was for Republicans, all of the post-game analysis indicated that it could have been even better. A handful of extreme Tea Party candidates like Christine O’Donnell in Delaware, Sharron Angle in Nevada, and Ken Buck in Colorado defeated mainstream Republicans in the primaries.

These Tea Party candidates caused the GOP to lose Senate races they had a real chance of winning in 2010.

In 2011, Republicans already in office feared that they too could be defeated in their primaries by more conservative Tea Party candidates. So they began incorporating the conservative ideas of the Tea Party into their platform and opposing President Obama at every turn.

With the presidential contest, we are now seeing the end of this phase of Tea Party blending into the GOP mainstream.

This means that Tea Party is effectively over as an autonomous movement in American politics. It is over because it succeeded in its primary objective of remaking the GOP in their image.

The best proof of this transformation is how quickly GOP candidates are willing to abandon moderate and liberal beliefs they previously held, in order to appeal to the base.

Mitt Romney and Newt Gingrich once supported the individual mandate in health care, now they oppose it. In the past, both said they believed in manmade global warming an supported a cap on carbon emissions, now they have switched. Rick Perry was for comprehensive immigration reform before he was against it. And the list goes on.

The one candidate who has been thoroughly consistent is Ron Paul, whom many regard as the intellectual godfather of the Tea Party movement. Earlier this year, I remarked that we were now living in the age of Ron Paul because of his influence in shaping Tea Party sentiment.

Paul’s surge into the top tier and the real possibility that he will run as a third party candidate signals that Tea Party movement has come full-circle.

In the Iowa Poll published in Sunday’s Register Paul wins a leading 42 percent of independents. The poll found a jump in likely-caucus attendance among people who call themselves Independent, from 13 percent in 2008 to 26 percent this year. Romney is second among independents with just 19 percent.

And Paul wins among people most likely to go to a caucus on several key questions such as who is the most knowledgeable candidate, most consistent, most dedicated to limiting government, cut the debt, reduce spending on war and least ego driven.

I keep hearing that because Paul’s views are so outside the mainstream that even if he wins the caucuses, his candidacy will be irrelevant. -- I believe this is grossly unfair to the Congressman and his supporters, who are the most committed and enthusiastic of any in the field.

A Paul victory in Iowa on Tuesday should not be understated but nor should it be overstated.
As Howard Baker once observed, Iowa’s primary function is to “winnow the field” of candidates. A poor performance in Iowa could force Bachmann, Santorum, Perry or Gingrich out of the race entirely and leave their supporters up for grabs.

In 1996, Dole won the Iowa caucuses with 26% of the vote but conservative firebrand Pat Buchanan came in very close second with 23%. This gave Buchanan the momentum he needed to win the New Hampshire primaries. Like Ron Paul, Buchanan tapped into the populist anger that fuels both the Tea Party and the Occupy Wall Street movement.

Dole went onto win the party’s nomination that year but his primary fight forced him to move further to the right and arguably made him weaker heading in to the general election against Bill Clinton.

Ross Perot ran as populist third party candidate, this time representing the Reform Party, siphoning off votes from Dole in key states and he lost the general election.

That year a vulnerable first-term Democratic president won re-election because of a lackluster, primary-worn Republican nominee and protest votes with a third party candidacy.

I wonder if history will repeat itself with Romney, Obama and Paul playing the parts of Dole, Clinton and Perot in 1996, respectively.

Juan Williams is a writer, author and Fox News political analyst. His latest book is "Muzzled: The Assault On Honest Debate" (Crown/Random House) was released in July.