WASHINGTON -- The tea party congressional candidates whose victories made 2010 a wave election for Republicans came to Washington united in their desire to slash spending, cut the size of government and place conservative principle over party loyalty.

During 21 months in office, tea party freshman lawmakers have endured detractors’ portrayals of them as ideological zombies who eschew compromise and engage in group-think. But the reality isn’t so simple: In dozens of key votes, the 68 new representatives who’d earned tea party campaign endorsements — all Republican — showed differences on a range of issues from fiscal austerity and defense spending to free trade, abortion funding and government aid for public radio.

“The desire to be independent is real amongst our folks,” Rep. Mick Mulvaney of South Carolina said in an interview.

The tea party lawmakers arrived in Washington in January 2011 under an election-fueled head of steam with an apparent mandate “to change business as usual” on Capitol Hill. They pushed their party elders to the right, their hard-line conservatism contributing to the gridlock that has helped make the 112th Congress one of the least productive ever.

Half of the 18 House members rated as the most conservative by the Heritage Foundation, a conservative think tank in Washington, are tea party freshmen.

But a McClatchy analysis yields a more complex picture.

Ten of the tea party newcomers voted against House Speaker John Boehner more than 10 percent of the time, an unusually large share for a freshman class. On one important vote after another — some 150 in all — they had to choose between competing conservative beliefs and among varying degrees of compromise. And as a result, the tea party contingent has scrambled traditional rankings along the conservative-liberal spectrum, skewing advocacy groups’ and news outlets’ traditional rankings of lawmakers.

The group’s most unyielding freshmen were rated centrist by outside groups because they voted with Democrats in opposing Republican bills that they said weren’t conservative enough. In an analysis of all 2011 House votes by National Journal magazine, for instance, freshman Republican Reps. Justin Amash of Michigan and Raul Labrador of Idaho were ranked among the 107 most centrist representatives, even though they are tea party heroes for their hard-core conservative stances.

Amash and Labrador joined Democrats in voting against a number of appropriations bills, but while the Democrats believed they cut spending too much, Amash and Labrador wanted deeper cuts.

“We must make drastic, across-the-board cuts to our federal spending levels,” Labrador said in explaining his votes. “We are headed to an unsustainable level of debt.”

Other tea party freshmen, by contrast, rank as centrists.

For example, Rep. Richard Hanna of Barneveld, N.Y., near Syracuse, who voted against Boehner 15 percent of the time, broke ranks on a GOP bill to oppose ending federal funding of National Public Radio, saying the legislation “amounts political censorship through the power of the purse.” The bill died in the Democratic-controlled Senate.

“Clearly, the tea party freshmen have been a force for limiting government in this Congress,” said Brian Darling, a Heritage Foundation analyst. “But just as clearly, there are differences within the tea party caucus over when to compromise.” Some members are libertarian-minded, he said, while others come from tough swing districts.