Thursday's first meeting of the Senate's Tea Party Caucus attracted four Republicans, and Ron Johnson was not among them.

The freshman Senator will not be joining the group at this time, an aide said.

"I sprang from the Tea Party and have great respect for what it represents," Johnson said in a statement. "The reason I ran for the US Senate was to not only stop the Obama agenda but reverse it. I believe our best chance of doing that is to work towards a unified Republican Conference so that's where I will put my energy."

In other words, Johnson does not appear to be interested in being part of a faction that may directly challenge the party leadership or prove divisive within the GOP caucus. His statement suggests that's a tactical decision, not a statement about his commitment to the Tea Party agenda (63% of Johnson voters last fall supported the Tea Party movement, according to the Wisconsin exit poll).

The four Republicans that were part of the inaugural meeting of the Tea Party Caucus in the Senate were: Jim DeMint of South Carolina, Rand Paul of Kentucky, Mike Lee of Utah and Jerry Moran of Kansas.

At the meeting, Demint thanked voters for electing three other GOP senators who have identified with the Tea Party movement but haven't joined the Tea Party caucus: Johnson, Pennsylvania's Pat Toomey and Florida's Marco Rubio.

According to this report, the absence of those three frustrated some Tea Party members.