Tea Party candidates seem to lack the momentum and, well, victory rate that they enjoyed two years ago, particularly with regard to Senate races. With four months to go until the general election, and several states yet to hold their state and congressional primaries, it's too early to declare the "death of the Tea-Party" movement. But the so-called Tea Party candidates have yet to claim the kind of wins that they did before.

It's tricky to formulate a hard-and-fast set of qualifications to identify a Tea Party candidate but, generally, there are a set of shared characteristics: the endorsement of Tea Party-affiliated outside spending group "FreedomWorks," which is a nonprofit that also has a super PAC arm; coupled with so-called outsider status; and an endorsement in many cases from politicians such as Sarah Palin or Rick Santorum who generally embrace the Tea Party movement.

By such a definition, only one Tea Party candidate has won the GOP nomination in their state's Senate race. Richard Mourdock, the Indiana state treasurer, defeated longtime Sen. Richard Lugar in the state's primary in May.

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Other candidates who were, at one point or another, considered strong contenders in GOP primaries ended up with relatively weak showings in their respective contests.

In Nebraska, state Treasurer Don Stenberg, once considered the strong challenger to the "establishment" candidate, Attorney General Jon Bruning, wound up finishing third in the GOP primary, with both candidates losing to state Sen. Deb Fischer. In Utah, Sen. Orrin Hatch defeated Tea Party challenger Dan Liljenquist by a margin of more than 30 percent, according to unofficial results from the Associated Press.

One big "establishment vs. Tea Party" primary has yet to take place. In Texas, former Solicitor General Ted Cruz, who is widely viewed as an up-and-coming Tea Party star and frequently compared to Florida Sen. Marco Rubio (both men are of Hispanic descent) is in the final weeks of a runoff with Lt. Gov. David Dewhurst, who is viewed as the establishment candidate in the race. Polls have consistently shown Dewhurst in the lead, but some political observers in the state believe that Cruz could benefit from the July 31 runoff, where turnout will be low and likely consist of a more steadfastly conservative demographic.

"My sense of this is that the Tea Party is traveling the route that we would expect historically for a movement of its sort" said Larry Sabato, director of the University of Virginia Center for Politics. "In the beginning it has more energy than it does two years later and two years after that. In part, it's because it's been very successful already and in part it's because over time, busy Americans lose interest."

Sabato points out that the expectations are different for the movement this time around as well, which can change the perception of the movement's success.

"In 2010, the assumption was that this new movement of amateurs wouldn't do very well and it shocked people by doing very well," he said. "Now, expectations are sky high and that changes the atmospherics for the Tea Party, and they're not going to repeat the victories of 2010. They've already gotten victories in a lot of the seats where one would expect them to be naturally competitive."

Hatch's victory in Utah might be the model for other "establishment" candidates going forward, particularly longtime incumbents. Hatch had the benefit of time. He watched colleague Bob Bennett get voted out of the running for re-election in favor of two Tea Party candidates at the state Republican convention in 2010, and he spent the subsequent two years preparing for a similar fight from like-minded challengers.

He didn't talk up his record of bipartisanship or his friendship with the late Sen. Ted Kennedy, D. Mass. Instead, Hatch highlighted things such as his history of support for a balanced budget amendment, and his push for the repeal of President Obama's health care legislation.

"Bob Bennett had to die so that Orrin Hatch would live," Sabato said. "Hatch got an early warning, which incumbents often need. If you think about it, incumbents as a group got an early warning out of 2010. The smart ones do what Hatch did, take nothing for granted.

"Don't make the assumption that people love you just because you've been in for a long time. Maybe more incumbents have taken that example to heart. They're all contrasting Bob Bennett to Orrin Hatch, and they've learned lessons from it."