Now that Mitt Romney has to take on both Rick Santorum and Newt Gingrich for at least the next four weeks, he’s about to take on plenty more baggage that he’d hoped to avoid — on social issues and perhaps on foreign policy.

Against just Gingrich, he could have run a split campaign, taking on Barack Obama on the economy while keeping Newt at bay by leveling sharp personal attacks against him. After all, the disgraced former Speaker has shown how vulnerable he is. But that’s not going to work nearly as well against Santorum, and it means that Romney is going to probably have to continue reviving his culture warrior act, with all that means for potential damage in November.

With that in mind, here’s a guide to the bumps ahead for Romney:

This weekend: Maine Republicans have been caucusing, and they’ll report the candidate-preference results on that day. There’s potential for another embarrassing loss for the Mittster if Ron Paul manages to sneak in a win there. There’s not much value for a Romney victory, since Maine is a small state in one of Romney’s home regions.

Also: CPAC, the big conservative gathering in Washington, is this weekend. While Romney might have wanted the luxury of launching his general election campaign there, instead he’ll be preforming a high-pressure grovel, as numerous neutral conservative opinion leaders will be watching him (and Santorum) closely.

February 22: Debate in Arizona. The first debate since Florida; again, another opportunity for Romney to pander to Rick Santorum’s core crowd of foreign policy uberhawks and social conservatives — but also another opportunity for Santorum and Gingrich to hit Romney on his liberal Massachusetts record, further sowing doubts among social conservatives nationally.

February 28: The winner-take-all Arizona primary and the winner-take-most Michigan primary. Two states that should strongly favor Romney; should things go wrong on that day, he really may be in trouble.

March 1: Debate in Georgia. The only debate leading up to Super Tuesday. With major battlefields in the south coming up, social issues again may take center stage.

March 6: Super Tuesday. Romney gets (presumably) easy wins in Massachusetts, Vermont, and, thanks to ballot follies, Virginia. It looks likely that he’ll face off with Santorum in Ohio, and Gingrich in Tennessee, Oklahoma, and Georgia; there are also caucuses in Alaska, Idaho, and North Dakota.

Bottom line: only in Ohio and perhaps Michigan will Romney get to keep on his preferred message of bashing Barack Obama on the economy. Everywhere else that’s competitive, the odds are that he’s going to have to talk still more about social issues, and that’s terrible ground for him in the nomination fight. Worse, instead of beginning his general election campaign now, Romney may be awfully tempted to make specific commitments on everything from marriage to birth control, promises the Obama campaign will be happy to exploit this fall.