SCOTT BROWN TARGETED BY HIS OWN SUPPORTERS…. Sen. Scott Brown (R-Mass.) narrowly won a special election in January in a reliably “blue” state, and it hasn’t exactly been smooth sailing this year. Brown has struggled badly to understand the basics of public policy, and many of his colleagues have come to see him as little more than an empty suit with a pretty face who’s in way over his head.

Still, Brown remains popular with his constituents and, thanks to a relatively moderate voting record, is well positioned in advance of the 2012 cycle, when he’ll seek a full term.

One of the senator’s more notable problems, at this point, is the activist Tea Party base that helped him win in the first place.

Senator Scott Brown’s decision to buck his party leadership in recent days on the “don’t ask, don’t tell” military policy and on a nuclear arms treaty has set off a new wave of anger among some of the activists who helped elect him — and renewed talk among conservatives that he might face a primary challenge. […]

[T]he threat of a primary challenge from conservatives — as well as the potential that national Tea Party groups will withhold financial support — appears to have grown, according to the movement’s activists. Brown’s votes in the past week follow his crucial support for the overhaul of financial regulations, which remains a particular sore point with conservatives.

“I think that there will be a primary challenge,” said Christen Varley, president of the Greater Boston Tea Party. “There’s enough of an underground movement in the Tea Party movement as seeing him as not being conservative enough. There probably will be multiple people who attempt to run against him.”

The Massachusetts director of the far-right FreedomWorks organization added, “We’re going to watch very closely over the next year and a half … and see if he’s going to be the ally that everyone had hoped it was going to be.”

It’s as if the right really did think it was electing a Massachusetts version of Jim DeMint.

I can see why the GOP’s hysterical base would feel some disappointment. Brown voted for DADT repeal, Wall Street reform, and New START ratification, and far-right activists were on the other side on each of these measures.

But Brown is running for a full term in Massachusetts. What’s more, he’ll be doing so in 2012 — when President Obama will be at the top of the ballot and Democratic voters will be turning out in greater numbers.

The very idea of the right launching a primary challenge seems bizarre, especially given the fact that there’s a weak GOP bench in the Bay State and Brown already has nearly $7 million in the bank. If the party’s priority is keeping the seat in Republican hands, Brown appears to be the obvious choice.

But as 2010 helps make clear, the GOP base doesn’t necessarily care about such calculations. As, say, the Senate race in Delaware helps make clear, right-wing activists aren’t necessarily concerned with who can win, or whose moderate temperament can work in a traditionally “blue” state. What matters is who meets the base’s ideological litmus tests.

Throwing some underfunded no-name at Brown would seem to be about as sensible as throwing some underfunded no-name at Mike Castle and Lisa Murkowski. But Tea Party zealots did just that in 2010, and may not have learned any lessons in advance of 2012.

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Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.