there are two ways to look at this:
(1) tea partiers are dumb. they don't seem to realize that their party only controls the house, and that the budget has to pass the house, senate and presidency to become law. that means in order for a budget to be passed, it has to be acceptable to a majority of the senate and to the president. because the senate has already rejected the house version of the budget and the president was against it too, that means they have to compromise. if they refuse to, the government will shut down and they will get the blame for it.although eric cantor's recent statements suggest that the answer might be #1, i'm afraid that the truth is probably #2.
(2) tea partiers are smart. they know if they hold the line long enough, the democrats will ultimately crumble and give in to most of their demands. that's what democrats do. unlike the GOP, the leaders of the democratic party don't give a shit about their base.