April will be a tough month for Rick Santorum.  The primary schedule has nine contests next month — three on Tuesday, a non-binding caucus in Missouri (again!), and five primaries on the 24th.  The two most likely states for a Santorum win are winner-take-all Wisconsin on the 3rd and the candidate’s home state of Pennsylvania on the 24th.  Santorum trails in the latest Wisconsin polling, and a new poll by Frank & Marshall College suggests that his support back home has declined significantly:

Rick Santorum appeared to be the Republican presidential candidate to beat in Pennsylvania a month ago.

With the state primary four weeks away, Santorum now finds himself nearly tied with former Massachusetts Gov. Mitt Romney among the state’s Republicans, and support is eroding rapidly, according to a Franklin & Marshall College poll out today. …

The poll of 505 registered Republican voters, conducted March 20-25 in conjunction with the Tribune-Review and other media outlets, shows Santorum clinging to a small lead over Romney, 30 percent to 28 percent, within the poll’s 4.2 percent margin of error.

That’s a big change from February, when Santorum, once a U.S. senator from Penn Hills, held a commanding 15-percentage-point lead over Romney in the poll.

This survey samples registered Republicans rather than likely voters, but since Pennsylvania has a closed direct election of delegates, only Republicans were surveyed.  The sample of 505 Republicans is significant enough to matter, although it will be interesting to see how well this aligns with other polls using larger samples of likely voters — say, Rasmussen or Survey USA.

What happened in the last month?  FMC reports that the importance of beating Obama has jumped ten points to 25% as the highest priority for voters.  Strong moral character still leads, but only barely at 26%, down from 36% in February.  The other two categories are “true conservative” (16%) and “the right experience” (21%).  That presents a muddy picture, and without crosstabs it’s difficult to see how this priorities played into voter choices.

On the surface, it makes it look as though voters won’t have much reason to choose between the two front-runners.  Santorum still gets higher favorables (54/26) than Romney (46/25), but that may change when Romney starts focusing on Pennsylvania after next Tuesday.  The other states holding primaries on the 24th are New York, Connecticut, Rhode Island, and Delaware — all states that Romney should win easily.  Romney can afford to try a knockout blow in the Keystone State in the three weeks open to him.

If Santorum can’t carry Pennsylvania, the race will be over.  Team Santorum had better hope this is an outlier.