Pat Toomey spoke at the group's inaugural meeting, but did not officially join.
The question is whether he won't join because he thinks it will be detrimental to re-election, or because he does not go all the way with tea party values. Indeed, one tea party value Toomey has dodged speaking about is auditing the Fed. He also supported the creation of Homeland Security as a congressman, which many tea partiers don't like.
Whereas Republican primary candidate Peg Luksik surely would have joined the caucus, Toomey only supports it.
Nevertheless, for the case of liberty, it's better that Toomey be in office instead of Sestak.
As of January 2011, the Senate Tea Party Caucus has 3 members:
Rand Paul (Kentucky)
Jim Demint (South Carolina)
Mike Lee (Utah)
3 out of 100 means 3% of Senators belong to the caucus.
The House's tea party caucus has 52 members, or about 12% of the members of House of Representatives.
Indeed, it may be more difficult for tea party candidates like Christine O'Donnell to make it to the Senate because Senators represent an entire state, and presumably, they on average have more moderate or liberal constituents than their colleagues in the House whose congressional districts may be composed of a smaller, more homogeneous constituencies.
Many Big Wig Republicans support the tea party at a distance because they realize that although the tea party may not be imbued with their views, tea partiers do speak for them on many issues, such as aversion to growing government debt, and therefore will vote for them. But many have complained that the GOP is trying to co-opt the tea party.