Published: Feb 28, 2012 9:23 PM EST

GRAND RAPIDS, Mich. (AP) - Rick Santorum is defending his campaign's use of automated telephone calls encouraging Michigan Democrats to vote against Mitt Romney today in the state's GOP primary.
    
Santorum is suggesting that Romney did essentially the same thing earlier this year, and that he should stop complaining. He says his campaign is doing what it needs to do to win the vote.
    
Romney told Fox news this morning that the phone calls are "a terrible, dirty trick." The calls urge Democrats to reject Romney because he opposed the government bailout of the auto industry.
    
Although the primary is only for Republicans, party rules allow voters to change their affiliation temporarily on the spot.
    
When he was asked today why he's struggling to win the support of his party's right wing in his home state of Michigan, Romney said it's because he's unwilling to say "outrageous things" like his opponents.
    
Neither Newt Gingrich nor Ron Paul has competed actively in today's primaries in Michigan and Arizona.
    
Santorum swept three states on a single night earlier this month. And another win, especially in the state of Romney's birth, would keep his momentum going.
    
%(at)AP Links
    
215-a-08-(Rick Santorum, Republican presidential hopeful, at campaign event)-"in Michigan tonight (cheers fade)"-Republican presidential hopeful Rick Santorum says he feels good about the Michigan primary. (28 Feb 2012)
    
<> 00:08  "in Michigan tonight (cheers fade)"
    
166-a-06-(Mitt Romney, Republican presidential candidate)-"our primary process"-Mitt Romney says its hard to predict the outcome of the Michigan primary because Rick Santorum has been calling Democrats asking them to vote. (28 Feb 2012)
    
<> 00:06  "our primary process"
    
165-a-11-(Mitt Romney, Republican presidential candidate, with reporters)-"a desperate campaign"-Mitt Romney says Rick Santorum is wrong to call on Democrats to vote in today's Michigan primary. (28 Feb 2012)
    
<> 00:11  "a desperate campaign"
    
217-a-05-(Rick Santorum, Republican presidential hopeful, at campaign event)-"the Keystone Pipeline (cheers fade)"-Republican presidential hopeful Rick Santorum says if he becomes president, the Keystone Pipeline will be built. (28 Feb 2012)
    
<> 00:05  "the Keystone Pipeline (cheers fade)"
    
APPHOTO OHBOW101: Republican presidential candidate, former Pennsylvania Sen. Rick Santorum speaks in Perrysburg, Ohio, Tuesday, Feb. 28, 2012. (AP Photo/Sentinel-Tribune, J.D. Pooley) MANDATORY CREDIT, TOLEDO BLADE OUT (28 Feb 2012)
    
<>

(Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)