Within the Tea Party caucus, Mr. Ryan is not the most absolutist. He voted for the TARP bailout of big banks at the end of George W. Bush‘s term. And he voted for the bailout of the auto industry. Both actions are anathema to some Tea Party lawmakers. And in some ways, he is not the Tea Party archetype. A six-term congressman who has worked in Washington his entire career, Mr. Ryan is an insider-type politician who works from within the system, not against it.

But as chairman of the House Budget committee, Mr. Ryan has resisted pressure from some in his party’s leadership to compromise with Mr. Obama’s administration in the interests of a grand bargain that many Tea Party members see as selling out.

And his far-reaching budget plans have attracted Tea Party support for the same reason that they have generated such fierce Democratic opposition: because they would go so far in reshaping the country’s long-standing fiscal obligations…

Three years ago, the Tea Party movement blossomed as a way of protesting Mr. Obama’s health care legislation. They followed up with a wave of political victories in the 2010 midterm elections that gave the movement a strong — if not always organized and coherent — voice in the Congress.