There's no shortage of tea party candidates challenging Republican senators this cycle. But they are almost nowhere to be found on the slate of speakers at the Conservative Political Action Conference that wraps up Saturday.

Milton Wolf (R), tea party Senate candidate in Kansas. (AP Photo/John Hanna)

The dearth of tea party candidates with major speaking roles at the annual confab is the latest sign of the struggles insurgent Senate contenders have experienced this election cycle. It's a also a departure from past years, when tea party candidates who ran against incumbents or candidates backed by the GOP establishment were featured more prominently.

Half the Senate Republicans running for reelection this year have primary challengers. And several of those challengers have been on hand at the conference, including Milton Wolf, the radiologist and second cousin of President Obama trying to unseat Sen Pat Roberts (R-Kan.). As The Post's Robert Costa reported, Wolf didn't have a speaking role and was looking for ways to meet with conservative activists.

Also spotted: Matt Bevin, Senate Minority Leader Mitch McConnell's challenger in Kentucky. Bevin was not on the lineup of official speakers. But McConnell did speak. And he stole the show on Thursday by wielding a gun onstage.

Tea party candidates in Senate races featuring Democratic incumbents and contested GOP primaries like Joe Miller of Alaska and Rob Maness of Louisiana have also been around. But neither of them gave speeches. (Maness introduced another speaker.) T.W. Shannon, a conservative candidate running for the seat of retiring Sen. Tom Coburn (R-Okla.) was there and spoke in a discussion about market capitalism.

But that's about it.

It wasn't always like this. In 2012, Richard Mourdock spoke at a discussion about conservative candidates before unseating Richard Lugar of Indiana later that year. Ted Cruz, then just a former solicitor general trying to spring an upset in Texas, also spoke.

In 2010, then-candidate Marco Rubio gave the keynote speech. He was on his way to forcing National Republican Senatorial Committee-backed Charlie Crist from the race. Now-Sen. Mike Lee (R-Utah) also spoke that year, his office said. Lee dislodged Republican Robert Bennett from the U.S. Senate in 2010.

A spokeswoman with the American Conservative Union, which puts on the conference, did not respond to a request for comment on the lack of tea party Senate speakers.

So what's going on here? As we've written, the tea party Senate field is wider than it is deep this year. There are a lot of candidates who want to be the next Cruz or Lee. But they all have their work cut out for them. Moreover, incumbents have heeded to the lessons from previous cycles. They are moving early to prevent their challengers from gaining the traction others did in 2012 and 2010.

In the one primary that is already in the books, Sen. John Cornyn (R-Tex.) danced to victory on Tuesday. A year ago, tea party activists were eager to take down Cornyn. But they never found a capable contender to challenge him and so he cruised.

Cornyn, by the way, spoke at CPAC.