The tea party movement, which established its power last year by defeating Republicans who didn’t meet their idea of what a conservative ought to be, is shifting to a more policy-driven focus as its leaders try to expand its growth and effectiveness. The strategy appears to be working, both on the presidential campaign trail, where most candidates are eagerly embracing tea party priorities, and in Washington, where loyalists are setting the terms of the debate over taxes and spending. On Capitol Hill, congressmen elected on the tea party wave of 2010 have helped grind to a halt negotiations over raising the debt ceiling with their objections to any deal that includes more taxes.