I think the reason the Republicans haven't done so is they've painted themselves into a corner by embracing the extreme views of the Tea Party concerning what type of people should be in power. Now they're realizing their mistake but there's nothing they can do about it.
Things are transparent enough these days and this new batch of Republicans is foolish enough that if the Republicans sent someone to tell him to knock it off, word of the matter would spread. Look at the Republicans, who supposedly hate career politicians these days, sending their career politicians to meddle in state affairs while they've been publicly advocating greater state power/minimal federal involvement. The Tea Party, for all their flaws, is more than willing to call the Republicans out and that sort of hypocrisy and at this point, that'll only cause them more issues.
Has Walker damaged things? No question about it. He set out to bust unions and Republicans talked about how this could've caused an end to 'corrupt unions' all over the country. Instead pro-union sentiment is as high as its been in years, anti-union legislation across the nation has had to be scaled back and more and more people are starting to see the current Republican Party as being too synonymous with far right, lunatic fringe types only interested in pushing an outdated political, ideological agenda that doesn't fix the country's problems.
But the damage has been done. Now they're better off either doing damage control from the outside or working to distance themselves from Walker type Republicans as they get closer to the 2012 elections.