With Senate Minority Leader Mitch McConnell, R-Ky., expected to cruise to a victory in the Republican primary on Tuesday, the media have already been framing it as a test of the influence of the Tea Party. But the truth is that for all of its influence in recent election years, the movement hasn't beaten a lot of incumbents in Senate primaries.

The perception that Tea Partiers were routinely knocking off incumbent Senators in previous years is a myth. The reality is that it's only happened a few times since the movement gained electoral influence. In 2010, incumbent Sen. Bob Bennett was ousted in the Utah state Republican convention, and Sen. Lisa Murkowski, R-Alaska, lost the Republican nomination but ended up retaining her Senate seat as a write-in candidate. In 2012, just one incumbent Republican, Sen. Richard Lugar, lost a primary -- in Indiana, to Richard Mourdock, who ended up losing in the general election.

In contrast to the three examples cited above (which include one sitting U.S. Senator), over the course of 2010 and 2012, there were 16 incumbent Senators who secured the GOP nominations in their states. Nobody would dispute the Tea Party influence over that time period, so it's silly see a McConnell victory as a referendum on the movement.

What's more significant is the fact that the Tea Party message on the size and scope of government is something that continues to carry a lot of weight, which is something that can get lost in the rush to brand candidates as being part of the Tea Party or from the establishment.

Because the Tea Party has now been around for a half a decade, non-incumbent Senators seeking higher office know that to be competitive in Republican primaries, they have to build up a record that can pass muster, and they've had opportunities to do so. That's how you end up with candidates such as North Carolina House Speaker Thom Tillis, whose victory in the Senate primary was branded as win for the establishment even though as speaker, he fought to block Obamacare's Medicaid expansion.

Eager to draw some broader lessons from a pretty boring Senate primary, the media have been trying to highlight McConnell's race as marking a shift in Republican politics in which the establishment is reasserting control. In reality, a McConnell win would be perfectly consistent with what has happened in most cases in recent election cycles, even as the Tea Party has had a strong influence.