Nine percent of voters in the Michigan Republican presidential primary identified themselves as Democrats, according to exit polling, the largest portion of the electorate the rival party has comprised to date in the GOP nomination fight.

View Photo Gallery: The GOP presidential candidates make their final push as primary voters in Arizona and Michigan head to the polls.

Former Pennsylvania senator Rick Santorum is winning self identified Michigan Democrats by a three to one margin over former Massachusetts governor Mitt Romney and Texas Rep. Ron Paul, numbers that suggest that the efforts by Santorum and the Democratic party in the state — talk about an odd couple! — is actually working.

Santorum’s campaign funded robocalls in the final days before the Michigan primary urging working class Democrats to cross party lines and vote against Romney.

At the same time, Democrats have done their best to urge party loyalists to meddle in the Republican primary and choose Santorum, who they believe to be a weaker GOP nominee than Romney. Democrats have dubbed their efforts “Operation Hilarity”. (Conservative talk show host Rush Limbaugh urged Republicans to crossover and vote in the Democratic primaries in 2008 to keep that race going, a plan he dubbed “Operation Chaos”.)

While the number of self identified Democrats is higher than it has been in any other contest to date — it was four percent each in New Hampshire and South Carolina — it is not the highest it has been in Michigan in recent elections.

Back in 2000, Democrats comprised 17 percent of the total Republican primary electorate; Arizona Sen. John McCain won that group 82 percent to 10 percent over then Texas Governor George W. Bush. McCain had significant support among Democrats and Independents in that race, which explains the large Democratic turnout.

In 2008, Democrats made up just seven percent of the Republican primary vote in Michigan; McCain beat Romney among that group by a more narrow 41 percent to 33 percent margin.

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