PERRYSBURG, Ohio- Flanked for the first time by Secret Service protection at an Ohio campaign event today, GOP presidential contender Rick Santorum defended his tactic of courting Democratic support in the Michigan primary and called his chief rival Mitt Romney a "bully."

Santorum accused Romney of winning in the New Hampshire primary earlier this year by accruing non-Republican votes in that state's open primary and then complaining about Santorum's appeal to Democrats in today's Michigan primary.

"If I appeal as a conservative to conservative Democrats, that's kidnapping the process?" Santorum said on the rope line after a campaign event. A reporter had asked about Romney's accusation that Santorum's robo-calls - phone messages to voters - aimed at Democrats was tantamount to kidnapping.

" Did you ask him whether the fifty-three percent of the people in New Hampshire who voted that weren't Republicans -  was that kidnapping the process?" asked Santorum? "He didn't seem to complain about it then. Thats what bullies do - you hit them back and they whine."

(Image Credit: Scott Olson/Getty Images)

In New Hampshire, Romney got 39 percent of the votes cast in the January primary. Fifty-one percent of the voters who took part were either Democrats - 4 percent - or Independents - 47 percent.

While he didn't win either group, Romney did gain votes from them. Jon Huntsman won the Democratic vote in the Republican primary with 40 percent to Romney's 14 percent. And Ron Paul won the Independent vote. But Romney was a close second with support from 30 percent of the Independents who took part in the New Hampshire Republican primary. Romney won the vote by Republicans in the New Hampshire Republican primary with 49 percent.

At his campaign event here e in Ohio, a crucial battleground state, Santorum today defended his tactic of  reaching out to Democrats to vote in the Michigan Republican primary. Santorum said his pro-growth message "is playing very well, hopefully, very today in Michigan."

"It's a message," he said, "we're selling not just to Republicans, but Republicans and Democrats who are the key for us winning Ohio and Pennsylvania and Michigan."

He said his appeal to conservative Democrats was akin to that of Ronald Reagan.

But Democrats encouraging a vote for Santorum in the primary said it was as a way to embarrass Romney and embolden a weaker candidate against President Obama.